This thesis focuses on the topic of the establishment and the classification of the functional urban areas (FUA) in Slovenia according the methodology of the project ESPON 1.1.1. In the first part of the thesis is presented the concept of polycentricity, its beginnings and historical development. More over are presented the national legal acts dealing with field of regional and spatial planning and guidelines for a polycentric spatial development. According the project ESPON 1.1.1., FUA are the building blocks of the polycentric spatial development. Slovenia, other EU members and a few more countries, that participated at the project ESPON 1.1.1. are supposed to establish and classify the FUA for the purpose of an effective evidence, further studies, strategies and other national needs. Methods of establishment and development of the FUA differentiate from county to county, because of diversities between them and other dissimilarities throughout the European area. Criterions for the establishment of FUA have been defined under project ESPON 1.1.1., as well as seven criterions for the classification of the FUA in the European area. In the thesis are presented the original method according the project ESPON 1.1.1., and a modified method for the Slovenian area and its special characteristics. FUA constitutes of municipalities. With the analysis of these municipalities there are also defined the characteristics of the FUA and their role and place in the Slovenian area and the wider European area. In the final part of the thesis are presented the collection and the analysis of data of the municipalities that constitutes the Slovenian FUAs, which have been classified according the modified method.