Political participation is a central component in all democratic systems, since citizen involvement is a prerequisite for assuring the lehitimacy of the system. Research on political participation has long acknowledged that this involvement cannot be restricted to elections. Nonetheless, the different institutional systems found in the established democracies create different possibilities and axpectations for citizen engagement beyond the vote. This goes not only for how much involvement is expected, but also for the ways in which citizens should be involved in political matters. In this study, the author examines how the institutional context affects various aspects of political participation in a comparative anallysis of 18 established European democracies. The aspects analysed include the dimensionality of participation, country-level differences in the rates of participation, the characteristics of the participants, and the institutional incentives for participation. The results suggest that the institutional context affects key aspects of political participation. However, the precise impact frequently runs counter to the theoretical expectations. The study hereby challenges some of the central theoretical assumptions of political science for how institutional openness affects patterns of political participation.