Abstract
Since the SEA Directive was entered into force, a most frequently asked question has been "whether the plan and programme at stake should be subject to SEA pocess or not". This question is supposed to be resolved by the SEA Directive itself and its Guidance. Yet, due to the unclear interpretation provided by the SEA Guidance, the diversity of decision making types among different Member States and the different industrial sectors, the application of it to plenty of cases remains unclear.