Mobility as a Service is a technology-enabled innovation recently introduced in the transportation sector and expected to bring many changes in the way people travel. In order to contribute to the emerging literature on MaaS, the present paper reports the results of a hybrid choice model, which takes into account the effects of service attributes, social influence attributes and individual attitudes on people's intention to subscribe to a MaaS platform. In addition, the findings of a mixed logit model that estimates individual preferences for bundle configuration are presented. The models are estimated using the data collected through a sequential portfolio choice experiment, which was the core part of a web-based survey undertaken in the Netherlands. The results highlight the importance of including latent attitudes in MaaS adoption choice modeling.