The aim is to treat the concept of social networks in tourism and their interaction, ie to show how social networks affect tourism, market and how they can help in the development of tourism and the promotion of tourist destinations. Tourism is today a popular activity of most people in the developed world, and the main source of income in many countries. It is very important how and in what way tourism is promoted because it greatly influences the choice of desired tourist destinations. One of the ways of promoting tourism in the world is advertising on different social networks. Decisions on the selection of tourist destinations are largely based on the information provided on social networks where human activity has become daily in the digital age. It is precisely here that it is possible to determine what is in the trend and which are the most desirable tourist destinations. Through this final paper I will present the most important social networks that influence the development of tourism on: Facebook, Instagram, YouTube, TripAdvisor, Pinterest and Twitter. They are not just social networks used for these purposes, but given the greater number of users and knowledge of these social networks, I have distinguished them. As an example of promotion of tourism on social networks, I have outlined the official profile of the social networks of the Croatian Tourist Board under the slogan "Croatia full of life".