This article presents some key research questions and discusses some advancements and controversies in the field of implementation studies in the European Union. In addition to calling for the further development of reliable quantitative indicators, the article suggests three issues worth considering. First, research could benefit from paying increased attention to the processes shaping the goals and aspirations in European implementation. Second, we should increase attention to the interplay between different explanatory mechanisms and in particular to the crucial roles of ambiguities and domestic capabilities. Finally, we should increase our interest into the study of outcomes and goal achievements, and thereby also offer critical and refreshing views on the dynamics of the actual European integration, as well as link this branch of research to the general research on legitimacy and democracy in Europe.