Along with progressive growth of urban population, and notably of those living in metropolitan areas as Lisbon, urban green areas are increasingly valued in their contribution towards the enhancement of quality of life and to the promotion of sustainable urban development. This metropolitan area is home to 3 million people who use the space for living, working and recreation. Depending on the location, as well as, the design, these areas are able to provide a wide array of environmental and social functions. Several recent studies on citizens' perceptions and behaviour towards urban green areas have shown the complexity and the multidimensional character of the man-nature relationship in the city. Therefore decisions on the planning and management of green areas in urban context require not only an ecological understanding of resources but also an understanding of residents' perception and values. Based on these considerations, this paper describes 2 exploratory studies: the first aims at identifying dimensions of perception and behaviour in green areas in Lisbon, and the second, based on the results of the first, has the purpose of building an attitudinal scale to evaluate the quality of green urban areas. The first, allows isolating a group of 6 dimensions, notably natural elements, security and maintenance, equipment, users and activities, evasion, urban quality of life. These results contributed to the construction of an attitudinal scale of 40 items (in the second study), which was applied to users of one of the most referred green area in the first study. By including questions in the first study concerning the preferences and frequency of use of green urban areas in Lisbon, it enables to identify associated behaviours and to link those responses to the quality of the spaces. Despite the fact that possibility of generalization the results is reduce by using a population of university students, it allows (for this age group) to identity a set of factors, organized in major dimensions that emphasise both the importance of the nature to the human being, as well, as the factors that contribute to the attractiveness and usability of green urban areas in Lisbon.