Abstract. The use of games in citizen science is growing, but can create tension as these can be seen as incompatible areas of activity. For example, the motivations of winning a game and the scientific pursuit of knowledge may be seen as contrary. Over a one-year period, we conducted a virtual ethnographic study of the public forums of two online projects, Foldit and Galaxy Zoo (GZ). The first where gaming is an explicit design feature and the second where it is not. The aim was to give a nuanced view of how participants topicalize and respond to tension between games and science. Thematic analysis of the forum posts showed that participants in the two projects respond differently to the tension. GZ participants highlighted the value of sharing and openness to sustain a healthy community while Foldit participants expressed concern for the project becoming the exclusive playground of an ever-decreasing elite group. For example, leaderboards were portrayed as antithetical to a healthy community in GZ as scores bring unhealthy competition and adverse effects on scientific validity. By contrast, the notion that ranking performance could be antithetical to the spirit of science was not part of the established community repertoire for Foldit. By unpacking participant responses to the tension between games and science, our study highlights that citizen science projects using games are not just about fun. In order to enrol and retain volunteers, they must also recognize and manage the implicit normative scientific ideals participants bring with them to a project. Marisa Ponti, Ph.D. Assistant Professor Department of Applied IT University of Gothenburg 412 96 Gothenburg Sweden Web site: https://marisaponti.wordpress.com/<https://marisaponti.wordpress.com/>