Extraordinary Ministers of Holy Communion may be used when the number of Ordinary Ministers of Holy Communion (bishops, priests and deacons) is inadequate for the purpose of distributing Holy Communion at Mass.

The General Instruction of the Roman Missal says, “The priest may be assisted in the distribution of Communion by other priests who happen to be present. If such priests are not present and there is a very large number of communicants, the priest may call upon extraordinary ministers to assist him, e.g., duly instituted acolytes or even other faithful who have been deputed for this purpose. In case of necessity, the priest may depute suitable faithful for this single occasion” (GIRM 162).