Canon law distinguishes the vicar general from two related offices a diocese may also have. An episcopal vicar exercises the bishop's ordinary power over only part of the diocese, a specific territory, a particular group of the faithful, or a defined area of church business, while the vicar general's authority extends over the whole diocese in general administrative and judicial matters. A judicial vicar, by contrast, heads the diocesan tribunal and exercises judicial rather than executive power, and canon law requires that the two offices be held by different people wherever possible. A diocese must have a vicar general, and canon law allows a bishop to appoint more than one when the diocese is large, each holding the same general executive competence rather than a divided portion of it.
The office ends automatically when the diocesan bishop's own governance ends, whether through death, resignation, transfer, or removal, and the diocese passes into a vacancy governed by its consultors until a new bishop is appointed and, in turn, appoints his own vicar general. In practice many dioceses also style the vicar general as moderator of the curia, coordinating the work of the chancery's other offices day to day, so the post functions as much as an administrative chief of staff to the bishop as a purely canonical deputy exercising delegated authority in his name.