This paper provides new empirical evidence on regional-national disparities in environmental efficiency, based on analyses of NAMEA data referring to Italy and the Lazio region, where Rome is the main city. Shift-share analyses provide evidence on the drivers of environmental efficiency and on sector specificity. This confirms the usefulness of this method, in order to investigate structural and efficiency factors at the level of within country environmental efficiency performance. Our evidence shows that although the region around Rome has achieved higher environmental performance compared to Italy mainly thank to its being less industry based, some critical points in the energy sector and in some services should be taken into account in shaping the future development of the region. In addition, the use of regional NAMEA for econometric investigations of emission efficiency drivers at national level shows that though north south disparities favour northern and richer regions, in accordance with development oriented dynamics, environmental hot spots driven by specialization and efficiency related issues also appear in some northern industrial regions. Further, the role of public ad private R&D is of main relevance in enhancing emission on economic value ratios.