Pieces of puzzle:empirical evidence and theoretical knowledge of the concept of Europeanization - The development and consolidation of the European integration has produced a visible impact on the political systems of EU member-states. As a consequence, since the second half of the 1990’s a growing 224 number of researchers has focused on the process of Europeanization that assumed the meaning of influence of European governance on national governance systems. The empirical and theoretical efforts have brought to important results. Currently, we have a wider and deeper understanding of the phenomenon, and a more powerful and complex conceptual and analytical framework for its study. Nevertheless, there is a lot of work to do. It is necessary to strengthen and put in a systematic and coherent scheme what we know and to discovery what we do not know. The article aims at giving an account of the research concerning the EU influence on national political systems; it highlights well-established findings, disputed insights and unexplored aspects of such a process.