This paper is focused on the fi rst ex-post analysis of the EU ETS in its 3 rd trading period in the Czech Republic, based on the analysis of the behaviour of the key EU ETS sector -combustion processes -and the decision making of Czech electricity and heat producers within the EU ETS. Firstly, the general overview of the EU ETS is presented, including the important scientifi c studies in this area. The characteristics of the EU ETS in the Czech Republic are described. The second chapter, methodology and data, describes the method, the questionnaire survey. The key chapter, results, focuses on the most important outputs obtained from the questionnaire survey. The discussion part deals with particular characteristics of the EU ETS in the 3 rd trading period in the Czech Republic. Focusing on the behaviour of Czech companies in the analyzed period, it is obvious, that the companies within the combustion processes group understood the EU ETS much more as an additional environmental tax or fee, instead of commodity, which can be traded on the exchange. Moreover, the EU ETS had no impact on their environmental investments planning in years 2013 and 2014.