SCETHALLER, Ján: Mystery shopping as a tool of evaluation of provided services in a selected company [Diploma thesis] – Technical University in Zvolen, Department of Marketing, Trade and World Forestry. Supervisor of Diploma thesis: Ing. Miriam Olšiaková, PhD. Degree of professional qualification: Engineer abbreviated „Ing.“. Zvolen: TU, 2021. 72 p. The aim of this diploma thesis is to evaluate the level of services provided in selected stores Teta drugstore using the mystery shopping method. The thesis is divided into theoretical and practical part. In the theoretical part we gradually characterize the terms market research and marketing research. Next, we define the term mystery shopping. We will describe how mystery shopping is realized and what types of mystery shopping we know. Then we characterize the state of mystery shopping in Slovakia. In the practical part we deal with mystery shopping in three stores of Teta drugstore in the Slovak Republic. We evaluate stores according to a pre-compiled questionnaire. Based on the results of the evaluation, we set proposals and recommendations for eliminating the identified deficiencies.