The omophorion has two forms: the ancient great omophorion, which passes around the neck, is folded in the front, and hangs down past the knees in both the front and the back, like a loosely-worn long scarf; and the small omophorion which is much simpler, passing around the neck and hanging down in the front similar to an epitrachelion (stole), only wider and shorter, coming down only a little past the waist. Because of the complexity of the great omophorion, and because of the dignity of the episcopal office, whenever the bishop puts on the omophorion or takes it off, he is assisted by two subdeacons.
Whenever he presides at any divine service, the bishop will be vested in the omophorion. If he is serving the Divine Liturgy he will wear both the great and the small omophorion at different times over his liturgical vestments. At any service other than the Divine Liturgy he will usually wear the small omophorion.
At the Divine Liturgy, the rubrics call for the bishop to put on and take off the omophorion numerous times. When he is first vested, the subdeacons place the great omophorion on him, but afterwards, when the rubric calls for him to wear the omophorion, it is replaced, for the sake of convenience, with the small omophorion. In some places, when several bishops concelebrate, it is now the custom for the chief celebrant to use the great omophorion when called for, and the other bishops to wear the small omophorion throughout.
In the Ruthenian Catholic Church and the Ukrainian Greek Catholic Church, often only the great omophorion is used. In this simplified usage, the great omophorion is not replaced by the small omophorion, and is worn by the bishop throughout the entire liturgy. In such cases, the omophorion is often sewn into shape and can be simply draped onto the shoulders rather than wrapped on by assistants. Some Ukrainian Greek Catholic Bishops, however, will insist on the full ceremonial.
During the All-Night Vigil, the bishop will wear the small omophorion at the beginning, but then near the end will change into the great omophorion for the Great Doxology.