Objective: Patients’ poor adherence to medical advice is a major obstacle to the effective delivery of health care. The present research focuses on how patient preferences and physician preconceptions may affect a patient’s decision to comply with a physician’s recommendation regarding flu inoculation. Methods: A 2 (physician’s recommendation: inoculate/not inoculate) by 3 (participant’s a priori attitude: pro/ neutral/against) by 2 (physician’s gender: male/female) by 2 (treatment setting: private/public) between-within-subjects design was used. One hundred eight-seven participants were asked to read four scenarios presented in random order, describing the circumstances that occur when visiting a physician who provides information about the possibility of flu inoculation. The participants’ a priori attitude toward this inoculation was then assessed. The key outcomes were the decision concerning flu inoculation and the certainty of that decision. Results: In general, the decision on inoculation was negative. The participants who a priori objected to inoculation made a more negative choice than those who had neutral preferences and those who a priori approved of it. Compared with a negative recommendation, a positive recommendation by a physician was associated with a less negative decision. The participants were more certain when deciding against inoculation than in favor of it. Conclusion: A positive physician’s recommendation caused the participants’ decision on inoculation to become less negative, but this suggestion was not sufficient to change the decision altogether. The participants’ a priori preference appeared to be a much more compelling factor in deciding whether to inoculate, and it also affected the conviction of that decision.