Studies of church architecture have often been unable to assign convincing functions to annexe rooms. This article attempts to address this problem by investigating the literary, epigraphic and archaeological evidence for such spaces, focusing particularly on western Palestine. This mainly concerns the role of a room identified from epigraphy as the diakonikon. Examples of such rooms with archaeological traces of furniture are explored, including installations for relics. Artefactual and textual evidence is also considered, revealing the changing function of these rooms, in terms of the preparation of the Eucharist, the storage of relics, the keeping of treasures and other items associated with the daily functioning of the church.