An analysis of the possibilities to form a trade enterprise's competitive advantage based on quality of service requires a diagnosis, to what degree that quality affects the level of attractiveness of the service for purchasers, and translates into results being achieved by chains. In result of the surveys carried out, it is assessed if the elements of the trade service, comprising quality thereof, are attractive for customers. Next, for the purposes of analysis, there are correlated synthetic measures of the trade service, calculated for every trade unit where the surveys were carried out, with income achieved by them. The calculated correlation coefficient evidences that there does exist a positive relation between quality of the service and trade enterprise's competitiveness.