The paper assumes that it is possible to make use of the notion of “common constitutional traditions” not only to fundamental rights (Art. 6,3 TUE), but also to institutional settings. It argues that the existence of such a common constitutional tradition can be envisaged among EU Member States, namely in the necessity of a trust relationship between Government and (at least one House of) Parliament. It has to be considered, in fact, that, with the only exception of Cyprus, in all the 27 Member States – although with many variations – a parliamentary or a semi-presidential form of government is provided. Therefore, the European choice is in favor of a “fusion of powers” model, requiring a mutual relation of trust between Parliament and Government, instead of a “separation of powers” one, which is dominant in other continents, such as America and Asia. This element needs to be taken into consideration also for correctly identifying the EU form of government.