Cette recherche, consacrée aux quartiers difficiles de la ville de Santiago du Chili, a pour objet d’étudier la vision que des jeunes habitants élaborent de leur espace public. L’étude a nécessité une adaptation psychosociale du concept d’espace public et l’élaboration d’un dispositif de recherche permettant de l’appréhender empiriquement. La recherche avait pour but d’étudier le rôle de la participation, ou de la non participation, aux associations de quartier (culturelles, éducatives, sportives, musicales, religieuses) sur la manière d’envisager l’espace public et se représenter autrui et les relations entre les habitants. Cinq quartiers déshérités de la ville de Santiago du Chili, distincts quant à leur histoire, ont constitué notre terrain d’étude et 45 jeunes habitants de ces quartiers ont été interviewés. La méthodologie combine l’approche qualitative et quantitative. Le corpus des entretiens a été analysé avec le logiciel Alceste. La participation aux associations s’avère être une variable importante dans la manière d’envisager la vie des quartiers et le rôle de différentes institutions qui y interviennent. Les représentations se distinguent selon le type des associations auxquelles ces jeunes prennent part. Cette recherche fournit des éléments pour réfléchir sur la pertinence des interventions en matière de sécurité publique, dont ces quartiers font l’objet de la part des autorités et les potentialités de ces jeunes habitants à modeler les relations quotidiennes et envisager leur avenir. Loin de se limiter à la réalité chilienne, ces questions concernent les phénomènes urbains dans une perspective internationale et constituent des enjeux dans les sociétés contemporaines. / The main purpose of this research, dedicated to the poor areas of the city of Santiago, Chile, is to understand the representation that young people develop of their public space. A psychosocial adaptation of the concept of public space and the construction of an empirical research device were needed. The approach is based on the study of concrete aspects of living in neighbourhoods with a special focus on identity and relational dimensions of the subject.Five poor neighbourhoods of Santiago city, distinct in their history, were chosen as fields of study and 45 young people living in these districts were interviewed. The main independent variable in this analysis was to distinguish whether young people were members of a neighbourhood association (and the kind of association: cultural, educational, sporting, musical, or religious) or whether they did not take part in any association.The methodology combines both qualitative and quantitative approaches. Semi-structured interviews have two parts: an oral description of the neighbourhoods, activities and social relationships with the illustration of remarks through the drawing of a socio-spatial map. In the second part, three scenarios evoking the difficulties of daily life were presented and the young people were asked to think of solutions to these difficulties. The corpus of interviews was analysed using the software Alceste. We were able to study their representations of others, social exchanges and various institutions involved in the life of the districts.The results have shown significant differences in the representations that these young people develop of neighbourhood life, their ability to have an impact on it and their perception of the future, according to the association activities they participate in.This research provides elements to reflect on the relevance of interventions in public safety, the potential of these young people to shape their everyday relationships and the representation of their living places oriented towards the future. Far from being limited to the Chilean reality, these issues concern all the major cities of the world and are issues specific to contemporary society.