Pain diagnostics and treatment are crucial components in the care of children with cancer. This study evaluated the extent and causes of pain, the use of methods for monitoring pain intensity, principles of pain management and adverse effects of pain treatment. In addition, care, support and information given to children and parents were evaluated. Structured interviews were conducted with 55 children with malignant disease and their parents. Pain was a common symptom and a major problem during different phases of cancer treatment and pain evaluation was unsystematic. Pain due to treatment and procedures was a greater problem than pain due to the malignant disease itself, and two thirds of the pain experienced by these children seemed to have iatrogenic origin. Younger children and children with short disease duration were more concerned about procedural pain. Parents and children thought that more efficient pain treatment was often possible. Parents claimed to judge their child's pain better than professionals, and children and parents wanted more information on different aspects of pain and pain treatment. Pain identification and treatment can be substantially improved through increased use of methods for pain evaluation and through giving enhanced information to families about pain and pain treatment.