This article discusses ethical and deontological issues of informing patients about cancer, which concern not only oncologists, but also doctors of other specialties. It is known that cancer is the strongest stress factor, therefore, competent and timely informing patients about this disease is of primary importance. Currently, a doctor who provides information about an existing disease is faced with the problem of overcoming ethical principles established in society, and also the need to comply with legal requirements. When solving this issue, a medical specialist should be guided by article 22 of Federal Law No 323-ФЗ of 2011, November 21, which states that every patient has the right to receive information about his health status in an accessible form in a medical organization. However, information about the state of health cannot be provided to the patient against his will, and in case of an unfavorable prognosis, the information must be given in a sensitive form to a person or his spouse or to one of the close relatives who were declared in medical records as allowed to be given such information. But, despite this, to overcome these difficulties, the doctor needs an individual approach to each patient, based on his/her professional experience. The peculiarity of informing patients about the disease, the degree of reliability of information should be determined by the specificity, type and stage of the cancer process, as well as the psychological, social and cultural characteristics of the patient, his age, gender, and profession. In addition, it is necessary to develop and implement state programs directed to improvement of cancer care and development of the social and psychological support services for patients suffering such pathology.