Two ingredients seem essential in understanding the patient-physician relationship: (i) the physician's informational advantage and (ii) the relevance of the patient's emotions. Health economics has placed great emphasis on the first phenomenon, whereas the second has been considered only recently, that is with the growth of fields of analysis such as Economics and Psychology and Behavioral Medicine, and few investigations have been undertaken. In this article, we survey and discuss the important changes of perspective which the theory that studies the patient-physician relationship has undergone over time. We focus, in particular, on the attitude of patients towards health information and on the role of patient information in physician agency.