The aim of the article is to characterized the theory of institutionalization of the region. Its author, Finnish geographer Anssi Paasi, described region as an effect of multiphase process that takes shape of an institutionalization. Such process starts when region has its territorial frame (territorial phase), then symbolic images are created and located in people’s consciousness inside and outside of the region (symbolic phase). In the next phase (called an institutional) symbolic images are transformed into formal institutions (law, strategies, organizations). In that phase regional actors operate in the field of a regional discourse. Region is a sociospatial phenomenon, a place where symbolic and institutional acting between different regional actors takes place. It is a constant process of legitimization specific images of regions, which is used to create a brand of the region and structuring the regional identity of people living in the region. The moment a regional identity and a regional brand is created by regional institutions is defined as a full phase of institutionalisation. Paasi’s theory is an important and interesting proposal, which can enrich the sociological surveys of the region, but it is necessary to supplement it. The process of institutionalization of the region involves all regional actors, Paasi argues that only formal organizations. Additionally, this process is dependent on the internal and external context and on the history of the region. These complements enriches heuristic value of the theory characterised in the article.