[Taken from “Orthodox Dogmatic Theology”, Vol. II, pg. 725]
The doctrine of the Roman Church on Purgatory has some resemblance to the doctrine of the Orthodox Church on the possibility for some sinners to be released from the bonds of Hades by the prayers of the living, although it has also some difference. To properly judge between the one and the other one must understand the teaching as set forth by the Roman theologians themselves.
I. They distinguish in the doctrine of Purgatory two parts: the ‘essential part’, or what has been decreed and taught by their church as dogma, and the inconsequential, that is to say, what has not been fixed by their Church and forms the object of theological opinions. The first part refers only to two points:
a) there is a purgatory, that is to say a place or state of atonement (status expiationis) in which the souls of those who died without having received absolution for even slight faults, or even after obtaining absolution for their sins, but without enduring in this life the temporal punishment for sins, suffer torment to satisfy Divine Justice, until they have been purified by these torments and have become worthy of eternal felicity.
b) the souls of those in Purgatory are in great need of prayer to aid them, such as alms, and especially the Bloodless Sacrifice.
As regards the non-essential teaching relates the solution of the following questions:
a) Is Purgatory a specific place or not, and if so, where is it? Are the sufferings of the souls in the purgatorial fire real or metaphorical?
b) How long are souls in purgatory? How are they aided by the prayers of the Church? (2)
II .— Stopping our thoughts on the essential part of the Roman doctrine concerning Purgatory, we find some resemblance to that of the Orthodox Church on the prayers for the dead, and at the same time some differences.
1) There is similarity in the fundamental idea. Indeed, the Orthodox Church teaches, like that of Rome: —- a) that the souls of some of the dead, namely those who died in faith and repentance, but without having had time to bring in life fruit worthy of repentance, and therefore, did not manage to receive from God complete forgiveness of their sins and be purified, undergo torments until they are deemed worthy of forgiveness and cleansed ; —- b) that in such cases the souls of the dead are benefited by prayers for them from those of their brothers in Christ who are still living, their works of charity, and especially the Offering of the Bloodless Sacrifice.
2. The differences, in particular, are: a) According to the doctrine of the Orthodox Church the aforesaid souls of the dead are suffering because, although they repented before death, they have not had time to bring forth fruits worthy of repentance, and therefore to deserve God’s complete forgiveness of their sins, and, thus, to actually be purified, and to overcome the natural consequences of sin, punishment; whereas, according to the doctrine of the Church of Rome, the souls of the dead suffer in Purgatory, strictly because they have not suffered here below the temporal punishment needed for sins in satisfaction of Divine Justice;. b) According to the Orthodox doctrine, these souls are purified of sins and deserve God’s forgiveness, not by themselves and of their own suffering but by the prayers of the Church and by the power of the Bloodless Sacrifice; with these same prayers not only benefiting the souls suffering, but mitigating their position, freeing them from the torment , whereas, according doctrine of the Roman Church, it is by their same suffering that souls are purified in Purgatory and thus Divine Justice is satisfied, and the prayers of the Church serve only to give them some relief in this condition. 
3) Moreover, although the differences between the Roman doctrine of Purgatory and the Orthodox doctrine of prayer for the dead are over these particulars, nevertheless, these are important, and we cannot accept the differences. For upon these differences we find both false things and a reversal of fundamental dogma:
a) the first idea is false, as we have already seen,  that is, that a sinner who repents before dying should still bring a kind of satisfaction to divine justice for his sins undergoing some temporal punishment for this purpose, and that in Purgatory, for lack of being able to suffer here below. Complete satisfaction to Divine Justice, the same superabundant satisfaction, was Presented once and for all, for all sinners, through Jesus Christ Our Savior, Who took upon Himself the sins of the world and all punishment for sin; and, to obtain complete forgiveness of God and freedom from all punishment of sin, sinners have to appropriate the merits of the Redeemer, that is to say, believe in Him, truly repent of their sins, bring forth fruits worthy of repentance, i.e., good deeds. Consequently, if there are sinners who, having repented before they died, have, despite this, torments to endure after death, it is only because they do not have time to fully appropriate the merits of the Savior, either because of the weakness of their faith in Him or by an effect of the failure of their repentance, and mainly because they did not bear fruits worthy of repentance, and were not actually purified from sin, as the Orthodox Church teaches.
b) it is no less a misconception that sinners would be purified in Purgatory and satisfy divine justice by their own torments. In whatever sense the fire of Purgatory is understood, either literally or in a figurative sense, in none of these senses can we ascribe this to God. If you attach a literal meaning to the fire, then, the fire by its very nature is incapable of purifying a soul which is a simple and immaterial spiritual essence. If you attach a figurative meaning, that is to say, the fire is an inner torment of the soul due to its consciousness of its past sins and the deep contrition for them, then, in that case, this cannot purify the soul in the life beyond the grave, because in the life after death there is no longer a place for repentance, nor for merit or any personal self-correction as Roman Catholics believe. And as long as the soul remains in sin, not purified and renewed, until then, whatever it may have to endure, it can in no way satisfy by its own suffering the Divine Justice and overcome these inevitable consequences of sin. 
c) If the souls of some of the dead suffer in Purgatory, even repentant sinners must necessarily suffer a temporal punishment for sin in satisfaction to Divine Justice, and, if the souls suffering in Purgatory are truly cleansed and meet their obligation to Divine Justice, then, the question is, “What is the point of prayers and the general intercession of the Church in their favour?” The souls in Purgatory necessarily have to suffer until they have fulfilled the desired satisfaction and have been purified by suffering; now, if the prayers of the Church only weaken and alleviate that suffering, instead of shortening the period of time that souls must pass in Purgatory, they (the prayers) prolong it and therefore are less useful than harmful. Does this not, of course, overturn the fundamental idea of the dogma of the prayers for the dead?
III. – If we now turn our attention to the non-essential part of the Roman doctrine concerning Purgatory, being theological opinions we find that it differs much more from the doctrine of the Orthodox Church on prayer for the dead, though on issues of little importance judging by their intimate meaning. Let us mention the two most remarkable:
1) The Orthodox Church teaches there is no intermediate class after death between those who are saved and go to heaven, and those who are condemned, and go to Hades; there is not a particular intermediate place where souls go who did penance before death and are subject to the prayers of the Church; all those souls go to Hades, where they can only be freed by its prayers.  Most Roman theologians consider Purgatory as a special intermediary place between heaven and hell, and sometimes placed in the vicinity thereof, in the interior of the earth, sometimes close to that one, sometimes in the air. There are others, however, who see in purgatory, not a place apart, but a particular state of souls, and recognize that the souls in this state can undergo their temporal punishment and be purified even where are contained those condemned to eternal punishment (that is to say, to hell); thus, there can be found in the same prison inmates sentenced to temporary imprisonment and prisoners condemned forever. (7)
2) The Orthodox Church strongly rejects the teaching of a Purgatorial fire, in the truest sense of the word, which cleanses the soul. (8) A great number of Roman theologians consider this fire as real and material (this being the almost universal belief of the laity of the Roman confession), and to garner proof of their teaching they attempt to collect from the Holy Scriptures and from the writings of the ancient Doctors of the Church references that seem to refer to such a fire (9). Others, however, understand the fire of Purgatory in a figurative sense, for spiritual torment, and therefore cite in their treaties on the subject similar evidence either from the word of God, or the writings of the Fathers, adding that the ancient Doctors themselves were of varied opinions on the fire (10). It would therefore be superfluous even to refute the evidence given. It is finally noted that in general their church has not determined precisely what the fire of Purgatory is, if it is material or not, and therefore it does not belong to faith to understand it in one way or another (11).
We will say nothing of other opinions concerning Purgatory, for example, how long a soul remains, and if they are all suffer the same space of time for the same penalties; what penalties they face; if they are more stringent than those of the present life and lighter than those of hell; if souls in purgatory pray for themselves and for us who are still in this world; if they give themselves up to the practice of good works, etc., etc. All these opinions have little value even to theologians of Rome and few seriously engaged themselves in answering them (12).
Notes from Metropolitan Macarius of Moscow’s “Orthodox Dogmatic Theology”, Volume 2, 1857, §259. S.463-467
1. Perrone. Praelectiones theologicae. Vol. III. 308-310. Louvain, 1839; Feier. Institutiones Theologiae Dogmaticae. VII. R. 41-47; Cursus Theologiae Completus VII. P. 1604 et squ; Liebermann. Institutiones Theologiae. V. Paris, 1839. P. 406-413
2. The Confession of the Orthodox Faith, Dogmatic Epistle of the Eastern Patriarchs, Part 1, Response 64.
3. At the Council of Florence this doctrine was expressed as: “Si vere poenitentes in charitate Dei decesserint, antequam dignis poenitentiae fructibus de commissis satisfecerint et omissis: eorum animas poenis purgatorii post mortem purgari, et, ut a poenis hujusmodi releventur, prodesse eis fidelium suffragia, missarum scilicet sacrifica, orationes….” (In Definit. Fidei.) [“If true penitents do depart in the love of God, but, before they make satisfaction by fruits worthy of repentance for things committed and omitted, their souls are cleansed after death by the penalties of purgatory, and, they are relieved from the pains of this sort by the suffrages of the faithful, that is to by the Sacrifice of the Mass, prayers…”]
4. Orthodox Dogmatic Theology, Vol. 2. §226-228, Concerning Penance and so-called “Indulgences”
5. Orthodox Confession, Response 66, Dogmatic Epistle of the Eastern Patriarchs
6. Orthodox Confession, Response 64, Dogmatic Epistle of the Eastern Patriarchs
7. Cursus Theologia Completus. T. VII. P. 1607; Feier. Institutiones Theologiae Dogmaticae VII. P. 42; Liebermann. Institutiones Theologiae. Paris, 1839. V> $!#
8. Orthodox Confession, Response 66, Dogmatic Epistle of the Eastern Patriarchs
9. Cursus Theologiae Completus. Locus citatus.
10. Perrone. Praelectiones theologicae. Vol.III. P.310-318,323,327; Klee. Manuel de l’histoire des dogmatiques. T.II.Paris, 1848. P.474
11. Bellarmin. De purgatorio. Liber II. S. 11 [Bellarmine. About purgatory. Book II, Chapter 11].
l2. Feier. Institutiones Theologiae dogmaticae VII. P.42-43; Cursus Theologiae completus VII. P.1068-1612.