A policy network approach has been developed to assess participatory policy processes in Ghana, Senegal, and Uganda. Theoretically, political influence measures correspond to two different influence mechanisms: vote-buying and informational lobbying. For each mechanism, separate measures were defined and empirically derived from corresponding policy networks. Exponential random graph models were used to assess the network-generating process, which allows for analysis of the robustness of the derived influence measures and the determinants of network structure. The results imply that participatory policy processes are dominated by donor and research organizations, while farm interests and civil society organizations have only a negligible influence. The design of stakeholder systems appears to be difficult since the observed network structures are mainly determined by relational factors that result from organizations’ social networking activities or other organizational attributes, such as reputation power, which cannot be easily controlled. Institutional factors such as membership in committees have only a minor impact.