The use of social networks in marketing is becoming increasingly more popular and is evolving continuously. One can certainly state that social networks play a large role in advertising today. In this thesis, the concept of social networks, their history and development have been illustrated. Social networks as communication channels which serve to send out a marketing message to the target group have been analyzed. Advertising models via most popular social networks as well as measuring their efficiency have been shown. Social networks have a great potential in advertising and it is important to use them cleverly in the way that they are being managed professionally and responsibly and that communication with users is regularly maintained. The aim of this thesis is to investigate the importance and determine the impact of social networks in the marketing activities of tourism companies. The purpose of this paper is to show how all social networks can be applied in the business of tourism companies and point out the importance of their role in the selection of tourism activities which would enhance their competitive advantage in the tourism market. In the last chapter, the importance of social networks in tourism has been explained, followed by a research conducted on a selected group of 70 people. The research used the method of analysis using a questionnaire completed by the respondents. The research has proven the hypotheses, whereby especially highlighting the importance of social networks when choosing tourist activities.