Fear of death, pain, or the recurrence of the illness of tumor patients can narrow their attention to a point where a spontaneous altered state of consciousness occurs. In these cases hypnosis either in formal psychotherapy or embedded into the everyday communication with the physician can effectively complement other already known medical and psychological techniques. Although numerous studies have reported the beneficial physical and mental changes induced by hypnosis, for a long time there were not enough research to affect evidence-based medicine. New studies meeting the most rigorous methodological standards, new reviews and the characteristics of hypnosis shown by neuroimaging techniques support the acceptance of this method. Hypnosis is used and studied with adult and child tumor patients alike mostly in the areas of anxiety, pain, nausea, vomiting, quality of life, mood amelioration, immune system and hot flushes. Most of the assays describe hypnosis as an empirically validated treatment technique that in most cases surpass attention diversion, coping trainings, cognitive behavior and relaxation techniques and other regular treatments. In this paper we review these observations.