We report 3 cases of anterior mediastinal masses in which we avoided providing general anesthesia for a biopsy and a central venous catheter placement. In all cases, chest X-rays on admission showed mediastinal mass ratio (MMR) greater than 44% and thoracic computed tomographic scans demonstrated cross sectional area (CSA) of the trachea 60% less than expected and the main stem bronchi narrowing. We made a decision not to provide general anesthesia, considering the risk of airway obstruction after induction of general anesthesia. In case 1, a 6-year-old boy, preoperative corticosteroid therapy relieved respiratory complaints without improvement of MMR and %CSA. On hospital day 3 the patient developed airway obstruction during induction of anesthesia and the surgery was postponed. After 3 days of additional chemotherapy MMR decreased to 34% and %CSA increased to 94%. On day 6 surgery under general anesthesia was performed safely. In case 2, a 15-year-old boy presented with MMR 44% and %CSA 48% and left bronchial stenosis and underwent surgery under local anesthesia. In case 3, a 3-year-old boy, preoperative corticosteroids and chemotherapy improved MMR 67% to 34% and %CSA 60% to 95%. On day 8 of admission a biopsy was performed under general anesthesia uneventfully. We emphasize not only clinical signs but also radiological signs are important to evaluate the safety in induction of general anesthesia for the management of the cases of anterior mediastinal masses.