As a main strategy of implementation of the new mental health policy (MSSS, 1989), regional plans of organization of services (RPOS) are put into effect in every region in Québec. This exercise in planning activities and mental health care aims at democratizing, decentralizing and redesigning the mental health system according to more diversified services. These RPOS also aim at improving integration of health care services, related activities as well as efficiency of this network. With a case study carried out in the Montérégie region and a descriptive analysis conducted in other regions, this article evaluates the validity and potential that these RPOS modify the mental health system along the lines of the new policy. The authors conclude to the relative structuring power of the planning instrument to regulate and transform organization of services given the scope of goals and its context of development. The article also questions the process of planning, decentralization and coordination related to the intervention. In a context where change is strongly claimed, strategies and mechanisms aiming at consolidating regional management are yet to be completed.