This study contributes to the understanding of citizen-government interaction in open government arenas by investigating why citizens are willing to participate in citizensourcing platforms. We draw on technology acceptance literature, motivation theory, and the theory of planned behavior to explain individual citizensourcing activity, and quantitatively test our hypotheses surveying users of an online reporting platform. Our results indicate that respondents who experience enjoyment when engaged in citizensourcing show a higher activity level. Open government attractiveness and perceived benefit of using citizensourcing platforms further explain high level of platform activity. Besides these factors, respondents who previously reported via traditional channels are significantly more active in online reporting. Offline reporting experience also positively moderates the relationship between perceived ease of use and online reporting. Quantitative analyses show, in addition, that individual motivation for engaging in governmental initiatives varies across proactive, interactive, and passive types of users. We conclude with implications for public managers operating platforms, and discuss future research opportunities.