With the 2004 eastward enlargement, the European Union became the largest common market in the world. The European Union, however, also became more heterogeneous as regards internal economic development levels. The new member states still have to reform their economies in order to catch up with the old member states. Both the widening and deepening of Europe, along with economic challenges in the new member states has important implications for the European political economy. Against this background, the European Commission financed the Young Researchers Enlargement Conferences (YouREC)-Project within the Jean Monnet Action programme. This volume presents a selection of the conferences' political economy contributions, dealing with the European Constitution, Europe's decision making efficiency, European monetary and fiscal policy, and regional integration processes.