This study evaluates potential for the reduction of greenhouse gas emissions in the passenger transport sector achievable through the use of mobility services. Beside car-sharing and -pooling, six services targeted at improving and encouraging the use of urban public transportation were considered. On the empirical basis of 42 in-depth interviews with representatives of previously identified mobility types (N=1991) and standardised mobility diaries quantifiable reduction potentials achievable through a shift to lower-emission transportation modes were revealed. The average reduction potential for greenhouse gas emissions per person and year was found to be 78 kg in an optimistic scenario and 25 kg in a pessimistic scenario. Extrapolated to the German metropolitan population, behaviour-related measures alone could result in a 1.8 million ton (optimistic scenario) or 0.6 million ton (pessimistic scenario) reduction of greenhouse gas emissions, respectively. In order to exploit this potential fully, however, target group specific information should be obtained and communication strategies developed, as addressed in this paper. This study further presents the limitation of reduction potential quantification against the background given by other studies of this rather unexplored issue.