The European Union embodies a particular type of political system and in the process of European integration numerous institutions and actors have emerged at a supranational, national and sub-national level developing their own interests. This paper analyses the cohesion policy, which is one of the most important policies of the European Union today, using the theoretical approach of historical institutionalism and the key concepts that appear in it – critical junctures and path dependency. The policy development is considered from the Single European Act, when policy gained the legal basis, up to the Lisbon Strategy, when the greatest enlargement in European history has occurred. It is shown that cohesion policy has a major impact on the development of the political and economic system within the European Union, with institutions and actors having to constantly adapt to respond to new challenges. Changes in the political system and cohesion policy have to be observed in the context of the creation of a single market, the Economic and Monetary Union, enlargement to the less developed countries and other processes within and outside of Europe. It can be noticed that the political system of the European Union is in permanent development, and cohesion policy represents a potential for a new form of European governance (the Multi-level governance). The European Union through cohesion policy promotes long-term sustainable programs and investments, while also because of the principle of solidarity, attempts to invest in less developed areas of Europe. The aim is to show that cohesion policy is becoming more and more important over the years and represents a new area within which various actors appear, with particular emphasis on the regions, which will be crucial for the efficient functioning of the political system of the European Union in the future.