More than a decade after the big bang enlargement, it seems that the European Union (EU) and its Central and Eastern European member-states have mutually adapted to one another. The debates regarding the historical implications of enlargement have now reduced in tempo and much of Eastern Europe seems to be an integral part of the European integration project. After the accession of Bulgaria and Romania in 2007 (and Croatia in 2013), and in light of the EU's internal troubles, enlargement has been sidelined from the EU agenda. The issue of the EU's performance in the "wider Eastern Europe" remains poignant, not least because of current developments in its "neighbourhood" (such as the crisis in Ukraine or Moldova's downturn from success story to a captured state), the uneven pattern of reform across some of the recently admitted states (such as the turmoil in Hungary and Poland or the ongoing monitoring of Bulgaria and Romania in the area of rule of law), and the evident slow pace of progress and even back-sliding in parts of the Western Balkans (e.g. Bosnia-Herzegovina, Macedonia). These cases, inter alia, illustrate that the EU's performance in the area is neither linear nor uncontested. Thus, questions regarding EU performance reoccur frequently and very often, its "transformative power" can be called into question. What determines EU performance in Central and Eastern Europe and in its Neighbourhood? What are the conditions that influence it? This collective inquiry addresses some of these questions. Much of the EU's own discourse puts emphasis on "performance" as a key driver of its policies and engagement with its partners (