Purpose: The aim of this study was to assess the validity of the factors which have influence on the Lean Service (LS) principles implementation process that serves to improve the organization and economics of district heating companies operating on the Polish market. For the purposes of our research the following research hypothesis was identified. Research hypothesis reads as follows: the greatest importance for improving the functioning of district heating companies is to minimize wastage identified in the processes of heat transfer is the attitude and behavior of management and employees. Methodology: Authors applied a diagnostic survey carried out in the selected trade industries. Findings: The authors characterized the basic assumptions of the LS conception, discussed LS implementation success factors, based on literature analysis. Assessment of the LS implementation level requires awareness of the supporting factors, that is LS implementation catalysts, as well as the factors impeding the implementation of this method. Studies carried out in the district heating trade enterprises made it possible to define the barriers that have arisen during the implementation of the conception principles in that type of companies. The authors evaluated the significance of the important factors that accompany the LS implementation. Assessing the significance of the effective LS principles implementation factors, which serves to improve the functioning of district heating companies, has revealed the most important factor, which is - according to the respondents - a focus on minimizing waste in processes. As a result of research the authors evaluated the intensity of particular waste groups in the surveyed organizations using the experts`` method, the experts of which were representatives of the surveyed enterprises. Several waste groups were identified and distinguished. They are for example: waste resulting from the employees passive behaviors, unused creativity of employees, unnecessary motion, waiting, office processes waste, data and information waste. Answering the question asked in the title of the paper - according to the research - you can ascertain that the effective LS conception principles implementation success factors are, in particular: the involvement of management in process improvement, staff attitude to minimize waste in processes, to reduce the energy used in the implementation of processes, the need to minimize costs, teamwork, and raising awareness of employees by investing in their competences (investment in people). The research resulted in the formulation of conclusions, one of which says that an effective remedy for the organization members passive behaviors can be Lean Behaviours. A detailed analysis of the Lean Behaviours assumptions may be the subject of another research project in this field; it is a new challenge for researchers who are interested in factors that support the implementation and realization of the LS conception principles. Originality: This is a first unique study on the topic of the Lean Service implementation success factors in the heat engineering. The achieved results can be useful for district heating companies as an guidance to improve management systems in those organizations.