After years of relative neglect, the role of private interest groups in European policy-making has attracted the attention of students of European integration once again. However, research on this subject suffers from the fact that the institutional peculiarities of the European Union, especially the integration of decision-making levels, have not been taken into account sufficiently. The crucial question addressed in this article is how the European system of joint multi-level decision-making affects the power and influence of private interest groups in European policy-making. It argues that, as a consequence of the new institutional framework, the logics of influence between public and private actors may differ significantly from the patterns of interest intermediation in domestic policy-making. Most interesting in this context seems to be the 'paradox of weakness', i.e. the fact that public actors can increase their autonomy vis--vis private interest groups as a consequence of their integration in systems of joint decision-making.