The Personal Assistant for onLine Services (PALS) project aims at attuning the interaction with mobile services to the momentary usage context. Among other thing, PALS should adequately address emotional states of the user and support users building up an adequate trust level during service interactions. In an experiment, participants performed interaction tasks with mobile services, on a small handheld device or a laptop. Before each task session, they watched film clips with different emotional impact (i.e. valence and arousal). In addition to performance measures, we measured trust and heart rate. In the handheld condition, task performance was substantially worse and showed a more extensive navigation path (i.e. more ‘wrong’ hyperlinks) to find the target information. Furthermore, during the experiment trust in the web services hardly increased in the handheld condition whereas trust substantially improved in the laptop condition. Device and service proved to be the major factors that determine the user experience. There is a clear need to improve the mobile interaction with web services in order to establish an adequate performance and trust level (e.g. by attentive interactive displays).