The thesis analyses the main issues posed by the implementation of Strategic Environmental Assessment (SEA) within the Italian physical planning system in the perspective of sustainable development principle, as elaborated in the supranational and European context. The proper implementation of the European Directive 2001/42CE in the national legal framework has revealed problematic as regards the definition of its scope and, specifically, the procedural patterns to be followed and guaranteed in order to ensure an high level of environmental protection in planning processes through early and effective integration of sustainability objectives in public decision-making. After more than ten years since Directive 2001/42CE adoption, sensitive issues still remain to be addressed in order to assess the effectiveness of the implementation both at legislative and administrative level. Taken previously into account the contents and main critical aspects of planning traditional discipline and practice, yet to be reformed at national level, the research work attempts to highlight the pre-conditions to be fulfilled for SEA proper implementation and the need of institutional adaptation of planning instruments and their relationships, in accordance with environmental systems complexities
