Non-institutionalised forms of political participation are on the rise in Western societies, but thus far, we do not know all that much about their effectiveness. In this article we report on the perceived efficacy of non-institutionalised forms of political participation, among both citizens and Members of Parliament (MPs). We draw on data of the 'PartiRep' (Participation and Representation) project, including both population data (in Belgium) and a comparative survey among MPs in Belgium and seven other European countries. The results show that both citizens and politicians still perceive voting as the most effective form of political participation. Consumer boycotts and illegal activities, on the other hand, were considered to be least effective. There is a rather large gap between politicians and citizens, however, with regard to the perceived effectiveness of contacting politicians and signing petitions. This mismatch between the perceptions of citizens and professional politicians might have important consequences for the legitimacy of the political decision-making process.