Voluntary programmes provide city networks with a central link to their city members. These voluntary programmes provide cities with benefits (e.g., knowledge, recognition, access to resources) if they meet the city network's programme requirements. This article seeks to understand how city networks make trade-offs between programme benefits and requirements to attract cities to the programmes they offer. We do so by analysing 55 voluntary programmes offered by 22 climate-related city networks using qualitative comparative analysis (QCA). We are particularly interested in the design of voluntary programmes that attract large numbers of participants. We find three main insights. First, programmes with a clear, single benefit are more attractive to city members than programmes with a broad range of benefits. Second, the combination of programme requirements and commitments allows city networks to target cohorts of cities based on their capacities and needs. Finally, cities are attracted to programmes that do not explicitly ask for direct results.