The behavior of parents may have a decisive impact on the child's adjustment to treatment. Their positive attitudes have a calming effect, support the patient's emotionally and overcome problems and bear sufferings involved in the treatment. Conversely, negative attitude may ruin the adjustment and provoke pessimism, lack of cooperation and even aggressiveness. Although the nature and degree of parental behavior and attitude may vary, their impact on pediatric patient adaptation processes shows a general trend. Of particular importance is the pattern of parental attitude at stages of treatment which involve frustration, extrapunitive behavior of parents being a possible negative factor. Our experience suggests that psychologists employed at children's oncological clinics should provide more counseling for parents and more training professional for the medical staff to improve adjustment of patients to therapy.