The aim of this study was to determine the factors to be taken into consideration while planning urban open spaces that are beneficial and appropriate for adolescents. It was targeted to determine the needs and demands of adolescents and the relationship of such needs and demands with open urban spaces. In the scope of the study, it was aimed to determine psycho-social needs of adolescents, which outdoor places they use in their leisure time and which activities they participate in. Behaviors exhibited by adolescents in selected city environments were examined in order to gather evidence regarding place preferences of adolescents and the way in which these places are used by them. In addition, affordances provided for adolescents by different urban environments (home environment, city parks, city centre, school surrounding, etc) were analyzed. These environments are the key environments of adolescents. The relation between the home environment, city parks, city centre and school surrounding preferences of adolescents and the affordances provided by these places was studied. Furthermore, opinions and demands of adolescents related to their own environment were studied so as to determine the kinds of affordances adolescents use in urban open places. Identity descriptions and leisure time preferences of 480 adolescents in 12-18 age range were examined. It was concluded that girls define themselves as "calm, active, tidy" while boys as "sportive, social and cool". Young people who participated in the study generally preferred spending their leisure time with their friends. Among urban environments, city centre was found to be the most-preferred environment by adolescents. Then, different urban places were evaluated by adolescents on the basis of 15 different affordances. It was revealed that city centre is mainly preferred for the affordances of shopping, recreation and being with friends; school environment for the affordances of trying new activities, obtaining new information and hanging out; home environment for the affordances of being alone, being with friends and shopping. City parks, on the other hand, are preferred for the affordances of being alone with close friends, being alone and learning.