Subject of this paper is focused on the multidisciplinary approach in studying the phenomenon of regionalization, which is conceived as the process of creation of lower administrative and territorial units within a state and transfer of central authorities to these units. Different concepts have been analyzed; the most significant characteristics of definitions: region, regionalization and regionalism have been underlined. Based on the multidisciplinary approach and method, four dominant models of regionalism in Europe have been defined: constitutional, strong, decentralized and administrative one. Regionalization concept has been considered in the dynamic way, within the historical context. Creation of European national states in the period between 17th and 19th century have been analyzed and centralistic state approach based on centralization and hierarchical vision of relations between central government and regions has been explained. Such approach has remained dominant in the territorial policy of national states until the last decades of the 20th century. The paper has presented historical path of regionalization in European countries with dominant models of regionalization e.g. Germany, Italy, France and Scandinavian countries as well as Spain, country with strong regional roots, which dated back more than couple of hundred years. Special attention has been given to analysis of different paths and contents of decentralization in European countries, starting in the 1970’s. Based on the analysis of contents of decentralization and regionalization and its constitutional and legal foundation it has been concluded that these processes represent significant step in further democratization of European countries.