This article deals with problematic aspects of the definition of relevant marketand the assessment of adominant position in the heating sector of the Czech Republic. The author analyses also apossibility to apply the essential facilitiesdoctrine with regard to athird party access in district heating networks. Incomparison to other European countries, there is ahigh utilization of district heating systems in the Czech Republic. Adistrict heating system is usually considered to be anatural monopoly and competition law problems in the industry havebeen often considered before the Czech Office for the Protection of Competition.The author refers in the article also to the decisional practice of the EuropeanCommission as well as to decisions of German and Slovak national competitionauthorities.