The paper starts with clarification of the elusive yet very important and topical concept of competitiveness by presenting its major characteristics. The main factors determining regional competitiveness are outlined. A model to assess regional competitiveness is then suggested, which is based on integrative criteria and makes possible the depiction of a comprehensive picture of the economic, social and technological conditions in the Bulgarian regions in a comparative perspective. In accordance with the availability of regional data, its quality and the theoretical considerations about the importance of the various regional competitiveness factors, a composite index of regional competitiveness is calculated. The aim of the paper is to determine the competitiveness of the 28 Bulgarian NUTS 3 regions and how it has changed in the years of European Union membership. Determining the relative competitive positions of the Bulgarian regions allows an evaluation of their current socio-economic situation, their strengths and weaknesses, and consequently extending recommendations for improvement of the country’s regional policy.