The purpose of this thesis is to find out how library staff perceives the impact of the introduction of lean on the operations focusing on users. In order to respond to demands from the library law and guiding documents, the Stockholm Public Library implemented an organizational change and introduced the lean management approach. The empirical data about the organization, lean, New Public Management, interviews, policy documents and the final report from the lean project were collected in the process of research. For a description and analysis of the empirical material the following theoretical basis was used: theory of change and a combined model of an organization's development created by Jacobsen and Thorsvik based on social psychologist Kurt Lewin's organizational change theory and political scientist Lars Erik Lyngdal's theory of development. Analysis of the results shows that the introduction of lean according to library staff perceptions influenced the operation's focus on users in different ways, both during the transition and afterwards. As for the utility and the results of the lean concepts and tools they generated in the operation, it was found that the informants were satisfied with the effects, and perceived that the tools generated a positive impact on the users' part. Study results and analysis show that lean can be used advantageously in public libraries but there are fundamental factors to consider when lean is to be implemented. Lean is seen not as the only management method that can be applied in public libraries but these should be chosen according to what works best in the organization.