Tuberculosis is a chronic disease caused by Mycobacterium tuberculosis, which usually affects the lung but may cause lesions in any organ or tissue of the human body. Mediastinal lymph node involvement is common feature of intrathoracic tuberculosis in children. Sometimes the lymph node may be enlarged and it causes compressive symptoms. Recently we experienced two cases of tuberculous abscess at middle mediastinum. The abscess seemed to be originated from the mediastinal lymphadenitis, and caused the symptoms. Operation was performed by median sternotomy and by posterolateral thoracotomy incision respectively for the purpose of relieving symptoms and diagnosing the mediastinal mass. The symptoms were relieved completely and postoperative course was uneventful.