The repercussions of European integration on national policymaking have increasingly drawn scholarly attention. Yet, the determinants of national adaptation to the EU are still poorly understood. This article takes issue with evolving arguments which grant crucial importance to the “goodness of fit” between European provisions and national rules and practices for explaining the degree of national adjustment to European requirements. In the implementation of the Packaging and Waste Directive in Germany, the Netherlands and the United Kingdom, the country with the greatest misfit, the United Kingdom, adapted more successfully than the country which only needed incremental adjustments, Germany. The German record was also worse than the Dutch one, despite the higher adaptation pressure of the latter. The finding of this case study draws attention to variations in the domestic institutional opportunity structures as explanation for the degree of adaptation to European requirements. Of particular importance are the institutional veto points that central governments have to face when imposing European provisions on their constituencies. The case study suggests that gaps in the goodness of fit are important as a major cause of domestic opposition, which is a necessary condition for variations in implementation records. However, the institutional opportunity structures ultimately tend to shape the pace and quality of implementation regardless of differential degrees in the goodness of fit.