In this article we examine the organisation of European policy-making in Belgium. The core question is whether the federal level is hollowing out in favour of the regional level, with respect to European preference formation and interest representation. From a theoretical point of view, it tests the propositions of liberal intergovernmentalism and multi-level governance in two critical cases: environmental policy and the European Convention. The article concludes that neither of the approaches is able to fully understand the complex system of joint preference formation that takes place in Belgium and that they would both benefit from incorporating historical institutionalist insights.