The aim of its introduction is threefold: We start from a conceptual clarification of preference formation, defining it provisionally as a political process ‘by which social actors decide what they want and what to pursue’. After an analysis of different conceptual and theoretical approaches, the introduction offers a critique of liberal intergovernmentalism, one of the major explanatory frameworks of preference formation in European Union studies. This critique centres on the context in which national preference formation took place during the European Monetary Union crisis. This special issue argues that the conceptualisation of preference formation as state-based, unidirectional and unchanged by the regime is deeply problematic. Preference formation is typically messy and non-linear and rarely closed to the possibility that both preferences and positions may change, sometimes radically, it is even more complex, context-sensitive, and open to a wide range of influences in a multi-level system such as the European Union. In other words, the traditional understanding of preference formation as a purely domestic process of interest aggregation and competition require revision given the multiple factors that shape preferences in general and in the interdependent policy-making of the European Union in particular.