Does the territorial state organisation matter for effective policy-making, and if so, in what way? So far, we know relatively little about its effects on policy making and policy outputs. Starting from the hypothesis that decentralised policy making has positive effects whereas federalism has a slightly negative impact on policy performance, this book systematically tests the independent and interdependent effects of different combinations of federal/unitary and decentralised/centralised structures of decision making and implementation. Based on a mixed methods design, it first quantitatively tests the relationships for the OECD countries in cross-sectional as well as panel designs. In a second step, qualitative case studies are conducted for four countries: federal-centralised Austria, federal-decentralised Switzerland, unitary-decentralised Denmark, and unitary-centralised Ireland. The authors study two space-related policy areas, both with regard to the decision making and the implementation stage of the policy-making process: regional policy and transport policy.The book represents a theoretically and empirically ambitious attempt to settle the persistent issue of 'does federalism matter?' Distinguishing between and combining the political-science focus on unitary vs. federal modes of policy making and the public-finance focus on centralised vs. decentralised modes of policy implementation, the authors seek to identify the impact of different configurations on the policy performance of OECD states.  On the basis of a great variety of quantitative cross-sectional and panel analyses and of matched case studies, they are able to show that decentralisation will generally have positive effects on policy performance, whereas the effect of federalism tends to be ambiguous or negative. This innovative study is bound to dominate debates in comparative federalism research for years to come. Professor Dr. Fritz W. Scharpf, Emeritus Director Max Planck Institute for the Study of Societies