This article aims to analyze, from a legal perspective, the boundaries of the obligation imposed on health care providers to inform the patient. This requirement originated and was developed as an ethical issue. However, with the newly approved law regulating the rights and duties of patients, the obligation to inform can be viewed from prisms and principles that differ from those governing medical ethics. With this purpose, we will focus on the comparative experience, which will allow us to evaluate the responsibility of health care providers when this duty is breached. We will try to answer the following questions: Which medical information must be informed to the patient? When should the doctor inform the patient? In which form should this information be provided?.