This paper focuses on methods for setting the monitoring systems of plans and programmes (plans), according to Dir. 2001/42/EC (SEA Directive). It proposes a systematic approach to correlate the indicators describing the plan implementation process and the environmental context indicators, in order to describe to which extent plans objectives and actions contribute to the achievement of environmental sustainability objectives set out in the SEA process. Essential element for the effectiveness of the approach to be used by public administrations is the set up of a shared knowledge base. Italian case studies are presented, highlighting opportunities and elements to be strengthened and showing tools developed.