This thesis is focused on the marketing research, namely by method of mystery shopping. This method is used for implementation of marketing research as a basis for benchmarking customer service area. The theoretical part deals with methods of benchmarking and mystery shopping, their substance, use, benefits and rules. As part of the theoretical part of the work is to outline the process of the internal training. The practical part deals with the realization of marketing research by method of mystery shopping using its results for internal and external benchmarking, which enables comparison of selected subdivisions within one company, but also with the closest competitors.