This paper reports on a meta-case study analysis of a 10 year research programme on citizenship, participation and accountability which analysed a nonrandomised sample of 100 research studies of four types of citizen engagement in 20 countries. By mapping the observable effects of citizen participation through a close reading of these studies, a typology of four democratic and developmental outcomes is created, including (a) the construction of citizenship, (b) the strengthening of practices of participation, (c) the strengthening of responsive and accountable states, and (d) the development of inclusive and cohesive societies. The report finds that citizen participation produces positive effects across these outcome types, though in each category there are also examples of negative outcomes of citizen participation. It also finds that these outcomes vary according to the type of citizen engagement and political context. These findings have important implications for the design of and support for participatory programmes meant to improve state responsiveness and effectiveness.