Public libraries are community spaces with a mission to provide access to knowledge, information, lifelong learning and works of imagination using a variety of resources and services. Performance of public libraries is aimed at customers and the entire community. In addition to providing access to knowledge, libraries are active in presenting their business to the community. With the arrival of new media - the Internet, promotion of library management, services and events, is greatly facilitated. One of the effective, free and creative ways to promote it is through YouTube. The marketing advantages of Web 2.0 tools will be discussed in the theoretical part of the paper. In the research part of the paper will be analyzed how public libraries are presented on YouTube. The main research method is the comparative analysis of the five YouTube channels of Croatian public libraries and five foreign public libraries. This paper analyses five aspects: how public libraries use YouTube in promotion, which content libraries present on YouTube channels, interaction between librarians and library users of YouTube channels and differences between promotion of public libraries in Croatia and abroad. The first part of the paper clarifies the main definitions and characteristics of Web 2.0, marketing and promotion of public libraries. The second part of the paper presents the public library through YouTube channels and examples of practice in Croatia and abroad. In the conclusion, the results of the research are presented, including examples of good practice and advantages and disadvantages of YouTube for library promotion.