As democracy arrived in Chile in 1990, so began the development of the environmental management process, whose objective is to contribute to the Sustainable Development of the country. In this respect, the main hallmark in environmental topics of the decade has been the setting up of Law 19.300, The General Law on the Environment. This law created the National Commission for the Environment (CONAMA), as a public service responsible for coordinating State bodies that have expertise in environmental areas, and it also gave the right to citizens to actively participate in all actions related to the care of Chile's environment. During these last years, different Regulations fundamental to State environmental management have been set up, among them being the Environmental Impact Assessment System, a process whose goal is to identify and evaluate the environmental impact specific projects or activities will have before they begin. Our work will highlight Chile's experience in the area of citizen participation in the Environmental Impact Assessment System. Our objective is to show the National Commission for the Environment's experience with this System from its inception in 1997 until now, the methodological advances achieved, and the new participation strategies now promoted by this institution. The latter will be illustrated through the description of two cases developed in the south of Chile, specifically in the Tenth Region, the Lake District. The first case deals with an industrial project, a Flour and Fish Oil Manufacturing Plant in the town of Corral, and the second is a Territorial Planning project designed in the town of Alerce.