In this paper, the authors enter into the issue of parliamentary development at the end of the twentieth century, as well as the contemporary tendencies of the relationship between parliament and the executive branch. The first part of the paper explains the problem of the legitimacy of the parliament through a theoretical analysis of the legitimacy of the government and the representation and participation of the people in that government. A brief look at the principle of separation of powers and its two basic models, the parliamentary and presidential systems, is followed by the overview of today's tendencies of the position and function of the parliament in the European Union. The first is a comparative overview of the former socialist states, and today full members of the European Union, which have all accepted the democratic achievements of the parliamentary system, of course to a greater or lesser extent, with certain oscillations. And then, since the parliamentary system is the dominant system of government in the European Union, its three variants in other European Union countries will be considered: 1) where, in relation to the parliament, the executive branch is strengthened in the person of the head of state, 2) where in relation to thr parliament the executive branch is strengthened in the face of the government or its president, and 3) where the parliament and the executive branch remain in balance.