The article starts a conversation in the literature about the governance structures of certain kinds of collaboratives in public management: public-private partnerships. The findings come from the study of implemented partnerships for regeneration and management of city centres in the U.S. (Business Improvement Districts) and U.K. (Town Centre Management), and the introduction of urban regime theory. A three-ideal typology is built up, concerning the roles played by structures/design of the partnership, legal frameworks, incentives, evolution, competition, governance structures, and the ways all of these evolve. The conclusion is that public-private partnerships are constantly evolving and may assume "variable geometries" in response to the form of governance dominating their internal arrangements. Partnerships may be of various kinds: symbolic partnerships, in which hierarchical governance predominates; instrumental partnerships, which obey market rules; organic partnerships, where the predominant form of governance is network-based. The kind of PPP employed affects how the relationship between public and private organisations is managed.