Book excerpt: The United Kingdom, Spain and Belgium have all undergone political devolution in recent years, with powers transferred from central government to regions and nations within these states. There is a rich literature on devolution, but surprisingly little on its consequences for public policy. This book explores the effects of devolution on the policy process, policy substance and policy outcomes in the UK, Spain and Belgium. The chapters study a range of policy spheres, including education, health care and general social policy, examining the scope for policy innovation and policy divergence between different levels of government. The analyses highlight the scope for comparison across devolved governments, which often face similar policy challenges and seek to exercise their autonomy within similar constraints. Each study underlines the importance of pre-existing policy communities, political cultures and institutions in shaping the scope for policy innovation within devolved governments. Each study also reinforces the need to consider devolved policy-making within the context of the nation-state. Devolution altered the relationship between the state and meso communities, but there remains a considerable degree of political and policy interdependence between governments at each level of the state. This book was previously published as a special issue of Regional and Federal Studies.