Complications of the mediastinal tumors and cysts are malignant change, infection, bleeding, local invasion and mass effect to heart, lung and other mediastinal structures. But early surgical excision and proper treatments bring patients to good clinical course and results. Therefore mediastinal tumors and cysts are surgically interesting diseases We report the analysis of the 58 cases of mediastinal tumors and cysts, experienced in the Department of Cardiothoracic Surgery of the Kosin Medical College from July 1979 to June 1989. The results were as follows ; Sex ratio of male to female to female was 1.3: 1. Range of age was from 11 to 64 years and mean age was 34.3 years. The thymomas were 14 cases[24%], the teratomas were 19 cases[33%o], the neurogenic tumors were 10 cases[17%], the cysts were 9 cases[15%], the carcinomas were 3 cases[5%], the thyroid tumor was 1 case[2%], the Castleman’s disease was 1 case[2%] and unclassified tumor was 1 case[2%]. Malignant tumors were 12 cases [21%] of the 58 cases. Most frequent symptom was chest pain and discomfort and relationship of symptom and malignancy was significant. Complete removal of tumor was performed on the 47 cases[92%] and partial excision was 3 cases[6%]. Inoperable cases were treated with anticancer chemotherapy and radiotherapy. Postoperative complications were wound infection, Homer’s syndrome, phrenic nerve palsy, mediastinal hematoma and pleurisy. There was no case of postoperative mortality and good clinical course in surgically completely resected cases.