If Strategic Environmental Assessment (SEA) to be effective and fulfil in the spirit of its governing EU Directive 2001/42/EC, cooperative and inclusive attitudes are essential. Cooperation should involve institutions, planning authorities and agencies which are involved in environmental assessment procedures. Inclusion implies favouring and catalysing local communities’ participation, that is participation of the public, in the planning/ assessment process.This paper discusses crucial aspects of SEA through a comparison of two case studies: the SEA of the Torbay Local Transport Plan 2006-2011 (LTPT) published by Torbay Council, and the Masterplan of the Port of the City of Cagliari, 2010 (MPPC) published by the Autorità Portuale di Cagliari in Sardinia, Italy, to provide evidence and lessons of good practice for both the UK and Italy. These include the assessment of:i. the endogeneity of the SEA process’ with respect to the planning process;ii. the sustainability and participation approaches;iii. the way available alternative planning options are compared;iv. the definition of the monitoring process.