Résumé/AbstractDuring the last few years, carsharing has undergone significant growth, both in Canada and around the world. In this type of service, users share access to a fleet of vehicles, thereby giving them most of the advantages of an automobile, such as its temporal and spatial flexibility, without many of the constraints of ownership. This article studies the geographical and socio-economic factors that favour membership of a carsharing service in Québec City. We combined Cervero's and Kockelman's 5D model (density, diversity, design, distance to transit and destination accessibility) with Hägerstrand's concept of innovation diffusion so as to analyze the evolution of potential carsharing membership. Zero-inflated negative binomial (ZINB) regression was used to model the spatial diffusion of the number of carsharing members in Québec City from 1996 (two years after its inauguration) to 2008 at the local scale with an annual time step. Results indicate that the carsharing distribution did indeed follow Hägerstrand's innovation diffusion model and that, even though some of the 5D model significantly influenced membership, it was the socioeconomic factors (education, non-motorization, and family structure) that most greatly affected the membership rate in the service area. The model is used to assess and discuss the market coverage potential in Québec City.