This research examines whether the extent of citizen involvement as co-producers in a local government network helps explain the relationship between a network’s structure (density and cliques) and its effectiveness. We developed a model and hypotheses based on the combination of two theories: Provan and Milward inter-organizational network theory and Ostrom’s polycentric theory of co-production. Our main premise is that specific organizational structures enable more citizen co-production which in turn enhances network effectiveness. A sample of 565 participants from 64 Israeli networks in a nation-wide youth at risk program demonstrates that the degree to which the network is divided into subgroups (cliques), not the network’s density, enhances the extent of citizen-users’ co-production, which increases network effectiveness. Theoretical and practical contributions are discussed.