Users often interact and help each other solve problems in communities, but few scholars have explored how these relationships provide opportunities to innovate. We analyze the extent to which people positioned within the core of a community as well as people that are cosmopolitans positioned across multiple external communities affect innovation. Using a multimethod approach, including a survey, a complete database of interactions in an online community, content coding of interactions and contributions, and 36 interviews, we specify the types of positions that have the strongest effect on innovation. Our study shows that dispositional explanations for user innovation should be complemented by a relational view that emphasizes how these communities differ from other organizations, the types of behaviors this enables, and the effects on innovation.