In this article the authors analyze from a theoretical point of view the process of the European integration as well as its internal and external dimensions. The study offers the definition of integration from etymological, economic and political views. There are analyzed the main European integration theories – functionalism, neo-functionalism, federalism, transactional and intergovernmental approaches along with institutionalism. Authors also pay attention to the difference between integration and cooperation and integration and adherence. It is underlined that integration is a long-term process within which states in a voluntary way lose a part of their sovereignty. Since the European integration is a complex process it is necessary to identify and analyze its main dimensions, both internal and external one. The authors mention that at external dimension the European integration refers to all developed and proposed European Union actions in outside, for both partners and states with European aspirations. The internal dimension of the European integration is reflected mostly at two levels, firstly by the domestic training of states that focus on obtaining of the European Union membership and phenomena of Europeanization and secondly of cohesion and thoroughness of integration between state members. It is mentioned that these two dimensions are interdependent and the main difference between them is that at internal dimension are created certain norms that are implemented in national systems, while at external dimension it is assured that the European Union rules and standards are transferred and adjusted by non-member states.