In the theoretical part of this thesis, it has been spoken about digital communication which became inventible part of present society. Society networking has changed the way of communication and connecting of modern society. The trend of social networks is integrated into every depth of society, on the private and business level. Companies use social networks to promote their products and services at a low cost, quick and efficient way in order to achieve feedback from users in a short time period. This thesis explained the specificity of using social networks as a marketing tool in business advisory Networking of users made collecting and sharing information easier and quicker. Networking of companies with respective users has become an important factor in online marketing because it enables personalization of relationship and optimization of business. With modern tools for determining target groups used in marketing, companies are able to target individual users with personalized content. In the thesis, it has been presented some of the most popular brands of protein products, from which the most significant MyProtein brand has the best ratio of quality and price according to the opinion of various experts, nutritionists, and athletes. Some of them are Marko Berić (eurepean champion in bodybuilding), Donat Rupčić (Fitness instructor in Zagreb) and Bojan Stojnić (master of nutrition). MyProtein products can brag about numerous awards and certificates for outstanding quality. The aim of the research was to find a connection between online marketing on social network sites and paradigm of users regards to products and services which are subject of online marketing. Important part of the research was to collect data which are going to be an indicator of changes in behavior of users during purchasing of protein products, driven by online marketing of protein products on social networks. Interpretation of results explained the importance of marketing on social networks and their impact on the purchasing market. In addition, data of protein products which II respective purchasers use the most have been collected. Research has been conducted on hundred random examinees, respective users of social networks. In conclusion of research and thesis, all adequate questions and explanations have been given. The result of research, although not enough precise to speak about the whole purchasing community, gives us good and detail enough picture. In conclusion of thesis „The impact of social networks on consumer decision-making when buying a protein product“ relationship between brands of protein products and trends of using social networks was explored. Brand recognition, effectiveness and simplicity are the main elements in the successfulness of this relationship. Recognition, due to positive ratio of price and quality Myprotein products, has positioned this brand on top of the Croatian market. Simplicity, speed and efficiency of online marketing through social networks made this type of marketing one of the most efficient. Combining quality products with effective marketing could be a ticket for the long-term success of a company.