Satisfied customers are an important advantage of almost every company. Every company tries to provide the best services to keep customers satisfied. The client must be satisfied, and in order to adapt to the requirements of the modern consumers and meet their expectations, numerous studies are conducted. Consumer behaviour includes pre-purchase activities, the purchase itself, and post-purchase activities. Since the decision-making process is influenced by many factors and it is subject to change, it is very important to constantly study consumer behaviour. Mystery shopping is a type of research tool for measuring satisfaction levels, customer experience in an unbiased way, and its goal is to improve the quality of services. This paper tries to reveal the conceptual understanding of mystery shopping, and it tries to explain the purposefulness of mystery shopping in various areas, whether public or private, and how it creates opportunities to improve company performance and customer satisfaction. For this purpose, a research was conducted in the paper, ie a mystery shopping in drugstore "dm" and "Müller". The methodology includes employee surveys, research and analysis of internal materials obtained from stores. The result confirmed that mystery shopping helps detect problems and truly affects consumer satisfaction. Also, the conclusion is that employees are the key category in measuring service quality.