The European Union sees the inclusion of many Eastern European states -enlargement- as a natural progression in the process of building an 'ever closer union'. For the European Commission in particular, the process of enlargement (broadening) is part of the process of integration and acts as a complement to the development of a stronger role for the European Union and its institutions or deepening of integration. Yet as the first Irish referendum on the Nice Treaty showed, not all of European's citizens see the two processes of enlargement and integration in the same light. This article addresses two related questions. First, how are attitudes towards deepening and broadening related, and do European citizens see them as complementary or contradictory? Second, and related to the first, what factors drive popular attitudes towards enlargement?