The book studies the development of think tanks and contemporary consequences in the United Kingdom, Germany, Denmark and at the EU-level. A Continental think tank tradition in which the state plays a pivotal role and an Anglo-American tradition which facilitates interaction in public policy on market-like terms have shaped the development of think tanks. On the basis of a typology of think tanks, quantitative data and interviews with think tank practitioners, the interplay between state and market dynamics and the development of different types of think tanks is analysed. Although think tanks develop along different institutional trajectories, it is concluded that the Anglo-American tradition has had a significant, cross-cutting impact in Europe in recent years. The contention over the politics of think tanks runs deeper at the EU-level than in the member states and reflects disagreement over how the EU should develop in the future.