This report examines the EU’s innovative climate and energy package: how this package of binding policies has been initiated, decided and implemented. From the early 1990s, EU climate and energy policies developed separately, despite efforts at coordination. Policies in these areas were based on different organiza¬tion, timing, policy instruments and objectives. In 2008, the EU adopted a package of climate and energy policies, harmonizing legislation to ambition levels unmatched by any other major actor in international climate policy. The present report argues that the linking of EU climate and energy policies can explain how differently-valued issues were combined, side-payments crafted to overcome distributional obstacles and synergies created to achieve a successfully negotiated outcome. Changes in circumstances can explain why synergies between climate and energy policies have been replaced by conflict and why this package may be a one-off event. Whereas issue-linkages can promote agreement, package deals may act to impede revision if circumstances change, as amending one component may have repercussions for the package as a whole. Stagnation or even disintegration of the EU climate and energy package may weaken the EU’s realization of a low-carbon economy and its ‘leadership by example’ in international climate policy.