From 1950-1986, a total of 159 children (age 1 day-16 years) were treated for primary mediastinal tumors at our hospital. There were 77 malignant and 82 benign tumors. Tracheal compression causing respiratory distress was a significant symptom in 45.3% (24/53) of the children under 2 years of age. The diagnosis was based on the chest X-ray and the findings at surgery. Malignant lymphoma was usually diagnosed by cervical lymph node biopsy (23/39) but the treatment protocol was non-surgical. Non-lymphatic malignant tumors were completely or partially excised in 59.0% (23/39) of the cases. There was no early or late mortality in patients with benign tumors. At follow-up (0.5-24 years; mean 6.0 years), 62.3% (48/77) of the patients with malignant tumors were alive and symptom free. About half of the mediastinal tumors in children are malignant. Mediastinal tumors in small children can cause severe respiratory symptoms demanding urgent treatment. The treatment of choice is surgery (except in lymphomas) and the results are good even in malignant tumors.