Since the adoption of the European Landscape Convention (ELC) in 2000, greater importance has been given to citizen participation in landscape policies and, specifically, in defining landscape quality objectives (LQO). Although the task of identifying and defining LQO is undertaken by professionals, the ELC provides for a compulsory public consultation. In most cases, no clear relationship between the results of public participation and the resulting definition of LQO and planning scenarios has been found. The objective of the present study is therefore to propose a methodology for designing landscape planning scenarios and defining LQO by the systematic, objective and quantified analysis of the results of a public participation process and taking advantage of the capacity of a Public Participation GIS (PPGIS) to capture public perception of landscape. The results of a picture-based survey and of the assessment of more than two thousand landscape scenes through the PPGIS allowed us to calculate indices of satisfaction and of the level of intervention required for each landscape type and area. From the values of these indices, four types of landscape planning scenarios were identified (protection, planning and management focused on protection and on planning), and the LQO for each landscape type and area were determined according to the resulting scenario. Application of the proposed methodology to the Landscape Guidelines for Galicia revealed information about the public perception of each landscape type and the preferred measures for landscape improvement involving protection, management and planning.