In this article the basic moral and psychological problems a doctor encounters in his professional relationship with a cancer patient are being discussed. That relationship should be mature one, humanistic and sincere. Unfortunately, in the reality it is most frequently an emotionally immature to a certain degree even insincere and thus deprived of its humanistic attributes. The reasons for such a situation are partly concealed in the very psychological problems a doctor might have, which is closely linked to his unconscious motivation for selecting this particular profession as his or her walk of life. The aformentioned problems must be seen in the light of a wide-spread fallacy that the patient need to be preserved from knowing the truth of their doomed state. However, in the same time, there is doctrinary attitude that instructs doctors to reveal all the details describing the situation realistically to the patient but in sincere, thoughtful, warm, humanistic way that can instill some hope to the patient's view on his illness. The mechanisms of phychological defense patients uses when faced to the truth are also being analysed, as well as all therapeutic preventive measures that should have to be taken in addvesing the same issue.