Internet-based crowdsourcing and co-creation platforms have changed the way how firms implement open innovation. They allow new participatory problem solving and value-creation processes. However, the current discussion on open innovation has hardly touched upon the public sector. This paper aims to shed light on what motivates citizens to engage in open government platforms. Surveying 437 citizens participating in the Bavarian open government project, our study reveals need for improvements as additional motive category, besides intrinsic interest like general political interest, or enjoying to meet like-minded peers. Although citizens' motives to engage in open government platforms largely resemble the motive categories of innovative users like open-source programmers or consumers to participate in co-creation projects, our results show some differences. Furthermore the identified motives significantly differ between active and less active citizens and have a different effect on participation behavior.