The increased frequency with which in trathoracic masses have been discovered in the pediatric age group seems to correspond to the increased utilization a typical location and appearance, the range of of possibilities is so great that the diagnosis is rarely made with any certainity before operation. For evaluation of clinical and radiological aspect of these tumors, we reviewed in pediatric age group 28 cases of primary intrathoracic tumor which were diagnosed pathologically at Severance Hospital, Yonsei University College of Medicine since 1971. The results: 1. The mediastinal tumors are predominent: 25 cases of mediastinal tumors and 3 cases of pulmonary tumor. 2. The incidence of tumors according to pathologic type is as follow: The malignant lymphoma is most common (12 cases, 45%), next is neurogenic tumor (7 cases, 25%), and Rhabdomyosarcoma 2 cases, benign teratoma 2 cases, thymoma 1 case, bronchogenic cyst of mediastinum 1 case. Pulmonary lesion as follow: 2 cases of al. mesenchynoma, and 1 case of bronchogenic cyst lung. 3. The sex incidence in out series shows male predominence (22:6) Under 6 years of age, neurogenic tumor and amlignant mesenchymoma are predominent, between 11 to 15 years of age malignant lymphoma is predominent and between 6 to 10 years age variable types of tumor are observed. 4. The radiological findings are as follows: a. Malignant lymphoma are located at the anterior and/or mid mediastinum with unilateral or bilateral mediastinal widening. The majority show smooth margin and lobulations on their borders. b. Neurogenic tumors are located in posterior mediastinum. Their margins are sharp or ill-defined. Specimen radiolography found minimal calcification in 1 case. Rib erosion and intercostal widening are noted in 2 cases. c. Thratoma are all located in anterior mediastinum with well defined smooth margin. Curvilinear calcification in 1 case. d. Malignant mesenchymoma are manifested as irregular shaggy bordered mass in lung p renchyme. 1 case show multiple granular calcification in the mass.