This study examines the relationship between the supply and demand variables that determine the probability of individuals joining a carsharing organization, using data from the Swiss National Travel Survey 2010 (demand) and the carsharing company Mobility (supply), located in Switzerland. Carsharing membership as reported in the Swiss National Travel Survey was used as the response variable for a discrete choice model (binominal logit), indicating that supply and demand variables are both significantly related to membership in carsharing organizations. By focusing on the relationships between the supply and demand factors, together with GIS mapping tools, potential markets for the expansion of carsharing in Swiss conurbations where demand is higher than expected based on the supply attributes (deviator groups) are identified. These markets are located in conurbations, are close to railways, support multi- and inter-modal life-styles and are suitable for the conventional round-trip model of carsharing. The results also suggest that individual preferences for transportation policies that aim at implementing mobility pricing for both public transport and car travel are positively related to carsharing membership. Therefore, we conclude that carsharing is not only an economic choice, but also a decision driven by a life-style involving sustainable mobility as a way of reducing infrastructure expansion.