Europeanization research has evolved into a promising research programme and has benefited from its increasing linkages with general theories of the social sciences. The paper starts from the assumption that the research programme would also benefit from a greater awareness of social science methodology. The paper focuses on the problem of case selection. Most Europeanization studies are designed in ways that the independent variables in which Europeanization research should be most interested EU regulations, incentives or models does not vary. Control cases are lacking. Therefore it is difficult, and some would even argue impossible, to demonstrate that the EU has been causally important for domestic developments. The paper explores two strategies to establish variation in the independent variable: counterfactual reasoning and comparing EU member states with non-members or, if research is restricted to EU countries, cases where the source of an EU effect is present with cases where the source of an EU effect is absent. Although neither of these strategies is a panacea for the problem of causality, their careful application will help to get better answers to the question of whether the EU makes a difference.