This article investigates the participation of interest groups in the EU's Constituional Convention and their contribution to the debate on participatory democracy and EU governance. I argue that the constitutional moment prompted interest groups to define their priorities beyond focused policy issues to include wider principles of governance. While the Convention process was more inclusive that any previous treaty reform procedure, its institutional set up was a constraint to improving citizen participation either directly or via interest groups. The Convention reproduced a model of closed elitist politics which did not communicate sufficiently with the citizens, while the role of interest groups was restricted by a Convention designed as a drafting phase in preparation for the real decisive phase during the IGC. Despite the impact of specific domestic contexts, the 'no' votes in France and the Netherlands proved that civil society and participation were rhetorical devices deployed during the Convention to gain legitimacy rather than a genuine move towards a more pluralistic EU democracy capable of deploying effective mechanisms of active citizen participation.