Nowadays social networking sites are commonly available and used by people in different age groups. These are used especially to communicate with other users but sometimes it turns into addiction, when people overuse it. This phenomenon belongs to so-called behavioural addiction which, only recently, has been described in scientific literature. It is crucial to differentiate when using social networking sites is normal and when it goes beyond the social norms. The article depicts the data concerning the spread of the social networking sites addiction phenomenon, its theoretical models and the possibility to identify it on the basis of diagnostic criteria offered by scientists. The main topic of this article is to discuss cognitive function in this specific kind of addiction. Researchers related this to personal, social and emotional spheres until now. However, it seems that cognitive processing, especially cognitive control and executive functions have a crucial role in explaining social media addiction mechanisms. Additionally, an understanding of these mechanisms can contribute to developing more appropriate forms both in terms of prevention and therapy.