The aim of this final paper is to analyse the social media communication of selected museums. Social media are some of the most popular public relation tools, and this research attempted to show how effectively it is used by the cultural institutions - museums in their communication with the public. A theoretical overview of key terminology is given, covering public relations, digital communication and social networks. Furthermore, this paper covers an overview of the museum’s communication on social media and its digital effect on communication. The emphasis is given to the research part of this thesis implementing a quantitative method of content analysis and qualitative method of structured in-depth interviews. The sample consists of three museums in the city of Zagreb – Museum of Contemporary Art, Museum of Arts and Craft, and National Museum of Modern Art, and the analysis covered Facebook and Instagram posts in the time period from 1st January to 31st March 2021. Structured in-depth interviews were conducted with the heads of the mentioned museums’ marketing and PR departments. This research aimed to find out how successful these museums utilize social networks to communicate through posts formats, user’s engagement and posts content. The results have shown that, even though the selected Museums are active on Facebook and Instagram, their posts engagement is low due to insufficient user management, low marketing budgets, but also the fact that the people running social media accounts do many other jobs as well.