Research has so far focused on what CSO involvement contributes to deliberation, participation and the emergence of a public sphere while we have no knowledge about such questions as who is actually represented through CSOs in EU policy-making, what are the grounds of the mandate claimed by the CSOs, what do they think constitutes their legitimacy, and more generally how can we think of non-electoral representation in the context of undefined constituencies beyond the nation state, and which is the EU institutional environment in which CSOs move? Identifying three ideal-types of political representation by CSOs, the empirical study draws on very fresh empirical evidence (2012) to analyze organizations active in the fields of agricultural, environmental and anti-poverty policy. It does so by combining qualitative (interviews, content analysis) and quantitative (questionnaires) methods. The paper concludes by discussing the potential and limits of what CSOs can contribute to representative democracy in the EU.