The concepts of sustainability and sustainable development have rapidly become usual, both in environmental sciences, and in everyday language. But the implications and motivations of these concepts have not rooted into citizen's minds. Our daily behavior doesn't seem to be affected by sustainability demands, and environmental problems depending on citizen's attitudes and behavior keep growing. In this paper, we assess the knowledge and attitudes towards sustainable development from a sample of citizens of Galicia, in northwestern Spain, and look for a diagnosis of the current status and connections between attitudes, behavior and knowledge about sustainability.