Collaboration has become a key element of governments’ efforts to address complex policy problems as well as of attempts to revitalise democracy. Depending on what public agencies want to achieve by engaging in collaboration – whether collaboration is intendedto gain support for public policymaking, induce voluntary actions by stakeholders, or something else – collaborative governance will have to mean very different things.Collaborative governance needs to be made fit for purpose. Drawing on the literature and a case study of road safety governance in Sweden, the article theorises on the interplay between strategic purpose and institutional design in collaborative governance and shows how two types of strategic purposes – policy support and voluntary actions – determine appropriate choices of institutional designs. This generates important insights that contribute to understanding institutional diversity and factors important to the success or failure of collaborative governance, and can aid practitioners who are designing collaborative forums within various policy fields.