This Working Paper presents novel data on the ‘quality of government’ (QoG) – understood as low corruption and as high protection of the rule of law, government effectiveness and accountability – at both national and regional levels in the 27 EU Member States. First, the Paper assesses the existing national-level data on QoG for EU Member States, pointing out the three significantly different clusters of states that emerge, namely high-, medium- and low-QoG countries. Secondly, the Paper presents original sub-national-level data for 172 EU regions, based on a survey of 34 000 residents across 18 countries. The two measures are then combined into the ‘EU QoG Index’ (EQI), which shows notable cross-regional variations: whilst highperforming regions in Italy and Spain (e.g. Bolzano and Pais Vasco) rank amongst the best EU regions, other regions in the same countries perform below the EU average. In addition, the Paper uses the new data to test five basic existing hypotheses on why some polities have more QoG than others.