We set out in this article to deepen our understanding of processes of comparative regional governance by investigating two historic regions (Wales and Brittany) in two neighbouring European Union states. We offer a framework for analysis that combines criteria drawn from institutions, relationships, identities, political opportunity structures, and environmental constraints and opportunities. If Welsh devolution is above all shaped by the institutional avenues opened in the Government of Wales Act of 1998, regional capacity in Brittany is built upon a dense network of relationships and tested forms of horizontal and vertical linkage. Political opportunity structures are vital for understanding comparative regional dynamics, notably the political space available for the development of a regionalist party, the interlocking of regional and social movements and the structure of incentives for regional players to engage in local, regional, national or European games. The linkage between identity, territory and institutions is primordial for comparing regions, the Wales‐Brittany comparison suggesting that politicized identities do not necessarily add value to regional political institutions. Understanding regional governance also requires cognisance of the overarching environment: the importance of constitutional rules, mechanisms of financial transfer, inter‐institutional linkages, the capacity of central government to intervene in devolved areas, or the Europeanization of specific policy sectors.