Abstract Investigating on transit users’ opinions represents a useful strategy to understand the level of quality of a service, and consequently pursuing the most convenient interventions for satisfying users and improving the service. On the other hand, an important issue for increasing the use of transit systems is linked to the necessity to attract new users, in addition to customize the current users. For this reason, it becomes fundamental to know also the perceptions of people who do not use transit systems with the aim to discover which are the reasons of their travel choices and particularly which are the most relevant transit service aspects for them. In this work, a Stated Preferences (SP) survey was conducted in order to investigate on both transit current and potential users’ preferences. This kind of survey allows potential users opinions to be captured due to its peculiarity of the possibility to propose to interviewees hypothetical services and not only real services, which could not be judged by people who do not use the service. The collected data were adopted to calibrate discrete choice models such as Random Parameters mixed Logit models and Latent Class models. These models allow heterogeneity of users’ opinions to be analysed. Calibrating this kind of models using data collected from both users and potential users permitted to capture the differences among users in their preferences about transit service quality, and the differences among potential users in their desired service quality. Model results showed some interesting findings concerning the differences of categories of users and potential users, and especially the diversity of preferences between people who know well the service and people who could become users even if they have not a real perception of it. We also calculated the Willingness-To-Pay (WTP), which allowed to discover that the WTP values obtained for the potential users are very much higher than the values obtained for the users. The proposed models can be also useful for the practitioners and transit operators to identify the best combination of the quality levels to assign to the various service aspects.