This study is aimed at determining whether the simulator sickness (SS) experienced by some drivers is influenced by psychological factors, such as cognitive solicitation, affective factors and a feeling of presence. We also wished to determine whether SS is caused by an individual reaction to the virtual environment (VE) itself or can be attributed to a more general personal predisposition. For this reason, we considered three conditions: driving a simulator, driving one’s own vehicle and driving a school-owned vehicle. Fourteen expert drivers participated in the study. Each drove under a different experimental condition and then responded to various questionnaires (SSQ, NASA-TLX and QPF). Our results showed that it is possible to identify at least three sources of explanation of why some people are more liable to feel sick in a driving simulator.