In recent years, after confirming that knowledge and training are valuable assets of organizations, different models and strategies that permit professionals to exchange and create knowledge with the aim of improving their abilities and work, are being promoted and established. This article describes two implementation experiences of communities of practice (CoPs) in the Catalan public Administration, pursuing a double aim. On the one hand, identifying in which way CoPs contribute to knowledge acquisition in the professionals involved; and, on the other hand, going into detail about the impact of the knowledge generated on the workplace. Results stem from the application of a 53-item selfadministered questionnaire to 175 participants, 40 in-depth interviews, 2 discussion groups and documentary analysis. Results show that CoPs participants establish a professional proximity by conversing and solving, in a consensus, shared work-related difficulties. CoPs make it easier to work on topics linked to the course of their work practice and learn in an informal way. Also, matters are clarified so that there may be greater exploitation and impact of the knowledge acquired on the workplace.