In modern studies of interest groups, three main types of interest representation are identified, each of which corresponds to one of the systems of political organization: pluralism, elite pluralism and neocorporatism. These types are determined by the role, priority, impact and involvement of interest groups in the political process. The European Union can be defined as a dualism of pluralism and neocorporatism. Such a system of political representation of interest groups is at the same time a balanced and dynamic one. This dualism of interest representation systems can be explained by the desire of the EU to increase the level of transparency in decision-making process and to overcome the democratic deficit. Analyzing the logic of access to the key EU institutions, the author highlights the structural and functional capabilities of lobbyists to influence decisions. The author focuses on the European Commission, European Parliament, Council of Ministers, the Committee of Permanent Representatives, the Economic and Social Committee and Committee of the Regions. Depending on the available resources and activities, interest groups lobby different institutions in order to ensure the adoption of favorable decisions for themselves. In this scheme, institutions represent a black box in which interest group requests are converted into concrete measures and actions. Therefore, to a certain extent, institutions are interested in interest group participation in the decision-making process. The institutional structure of the European Union is heterogeneous: not only do the institutions themselves differ from each other in their policy, but they often lack coherence within their own structures. Hence, lobbyists have to adapt to each institution separately and find specific approaches and methods of interaction. However, the European Commission does not seek to use strict measures of control in relation to interest groups because they are the main source of information and expertise. On the contrary, the Commission encourages the development of networks between interest groups whose positions have something in common. These are the main features in the logic of access to the EU institutions.