Public participation is a popular mantra in contemporary governance. Participatory mechanisms have been analysed extensively. The systematic study of how, where and why public authorities implement them is, however, under researched. The paper aims to fill this gap by focusing on participatory budgeting (PB) processes in the Belgian context (Wallonia and Brussels). First, we critically assess the ‘participatory’ feature of PB by comparing who decides in such processes. Second, we identify the contextual and political factors that trigger the establishment of PB. Findings suggest that PB has become a widely diffused institutional practice for authorities with different ideological orientations and across different municipal contexts. However, the way the participatory ideal is put into practice reveals distinct dynamics. In some cases, the use of the participatory rhetoric is a way to requalify an old practice without significantly transforming how the budget is allocated. Overall, this study seeks to offer a ...