Kolektywne emocje w grupach internetowych [Collective emotions in cybercommunities] Janusz Hołyst (Center of Excellence for Complex Systems Research, Warsaw University of Technology) Emotions are an important part of most societal dynamics. As with face to face meetings, Internet exchanges may not only include factual information but also emotional information; how participants feel about the subject discussed or other group members. The development of automatic sentiment analysis has made possible a large scale emotion detection and analysis using text messages collected from the web. Here it will be shown that emotions in on-line groups can possess a collective character due to sentimental interactions between group members. It seems that negative emotions frequently drive the community live and in the course of time probabilities of various emotions tend to equipartition distributions. An agent-based computer simulation model has been developed to reproduce several essential characteristics of the analyzed system. Based on: [1] A.Chmiel, P.Sobkowicz, J.Sienkiewicz, G.Paltoglou, K.Buckley, M.Thelwall, J.A.Hołyst (2011) Negative emotions boost user activity at BBC forum, Physica A 390, 2936-2944 [2] A.Chmiel, J.Sienkiewicz, M.Thelwall, G.Paltoglou, K.Buckley, A.Kappas, J.A.Hołyst (2011) Collective emotions online and their influence on community life, PloS ONE 6(7), e22207 [3] J.A.Hołyst, ed. (2016) Cyberemotions: Collective Emotions in Cyberspace, Springer