When the Lisbon Treaty entered into force on 1 December 2009, no one quite knew how this would impact transatlantic relations or how an EU with increasing responsibilities would act toward its neighbors. In the months since, we have seen successes and setbacks: Implementation of the Lisbon Treaty is progressing within the EU with a new President and High Representative already in office, yet transatlantic tensions over the sharing of SWIFT data have called internal EU cooperation into question. In Policy Report 44, authors Frances Burwell and Ludger Kühnhardt examine the Lisbon Treaty and discuss what its influence will be not only on the EU, but also on transatlantic relations and the EU’s neighborhood.