In discussing the normative implications of the doctor-patient relationship, medical ethics has mostly focused on the duties of doctors to their patients. This focus neglects an important normative dimension of the doctorpatient- relationship, namely the duties of patients to doctors. Only few authors have discussed the content and ground of the moral duties of patients, and each of these accounts are wanting in some way. This paper discusses patients’ duties and argues that patients have a relationship-dependent obligation to cooperate with the doctor, because doctors have a morally justified interest in fulfilling their moral role obligations as doctors, and by not cooperating, patients make it more difficult for doctors to fulfill their moral obligations. In some cases, failing to cooperate might even create an avoidable moral dilemma for the doctor.