The subdeacon's essential role is to assist the [[bishop]] during a hierarchical [[Divine Liturgy]] (a Divine Liturgy at which a bishop is present and presiding) by [[vestments|vesting]] him, holding his service book, carrying his staff, presenting him with the [[dikiri]] and [[trikiri]], etc. There is a special service for the [[ordination]] of a subdeacon, although in contemporary practice an [[acolyte]] or a reader may receive the bishop's blessing to vest and act as a subdeacon, either for a particular occasion or permanently. The main reason for this practice lies in the fact that the canons (e.g. , Apostolic canon 26 et al.) prohibit subdeacons to marry after their ordination (just like deacons and [[priest]]s). This latter stipulation has sometimes led to the reservation of the formal ordination service to candidates for the priesthood, although this is not universal.

Although the [[canons]] stipulate the subdeacons may not [[marriage|marry]] after their ordination to the subdiaconate, in modern practice, some churches allow them to marry. (As with many canons, the way this one is applied varies.) The subdeacon is vested in a [[sticharion]] with an [[orarion]] tied around his waist, up over his shoulders (forming a an X-shaped cross in back), and with the ends hanging down in front, tucked under the section around the waist. Like readers, subdeacons are permitted to wear a [[cassock]], although many only do so when attending services.