This paper discusses the possibilities for using social media in promoting public library services and describes the changes that occurred between 2011 and 2013. The results of an analysis of a group of Polish urban public libraries for the occurrence of Web 2.0 elements and social media references are presented. Quantitative analysis included the number of Web 2.0 elements in pages, the number of references to social networking sites and the number of users of various types of Web 2.0 library profiles. Qualitative analysis concerned the extent and type of information shared through social media. This article presents the scope of changes that have occurred in the use of Web 2.0 elements by Polish urban public libraries in recent years, as well as prospects for the further use of social media. It also shows the dynamics of change in terms of how public libraries use Web 2.0 services. This comparative study shows that over the 2 years studied the number of libraries using social media increased, as did the variety of tools and the frequency of their use. The study was conducted using a specific sample of public libraries in urban areas in one Polish province. The study is not representative of all public libraries in Poland. However, the author believes that the study shows certain trends that may be characteristic not only of libraries in the studied region, but also across the whole country, and the results could be widely used in practice to improve social media activity.