The building sector consumes the largest part of common final energy consumed in the European Union and therefore this sector has a huge potential for reducing the energy consumption. Part of the strategy which aims to limit the use of energy in buildings represent in 2002 adopted Directive on Energy Performance of Buildings (2002/91 / EC) and revised EPBD Directive 2010/31 / EU which is an upgrade of the first one and sets some further strengthened requirements. Additionally to the provisions targeted to these objectives, the Directive prescribes the introduction of an energy performance certificate of building. The energy performance certificate is a document containing the information about the building energy performance including recommendations for increasing the energy efficiency. From January 1, 2015 the energy performance certificate of building is obligatory required in Republic of Slovenia when selling the entire building or a part thereof and when renting a building for a period of one year or more. The main purpose of this thesis is to examine the impact of energy performance certificates of buildings on the real estate prices in Republic of Slovenia in the period after its enforcement. The first part of diploma thesis presents the general information about the energy performance certificate of building and includes an analysis of four studies that provide key findings in the field of energy efficiency of buildings and the impact of energy performance certificates of buildings on the real estate prices in other countries. Research in other countries has shown that energy performance certificates of buildings have some impact on the real estate prices. In following part the public opinion survey by using a questionnaire is presented. By means of the questionnaire we analysed the impact of energy performance certificates of buildings on the real estate prices in Republic of Slovenia and the public attitudes towards the energy efficiency of buildings. The data obtained were analysed by using the SPSS program and some results were compared with other studies. We found that the energy performance certificates of buildings (so far) have no major impact on the real estate prices as in Republic of Slovenia the energy performance certificates of buildings do not have the tradition yet. However, the buyers of the buildings are slowly starting to consider the data on the energy classes of buildings.