General anesthesia for the removal of a large mediastinal mass has been associated with life-threatening airway obstruction. We present a case of general anesthesia for a patient with superior posterior mediastinal mass and critical airway compression who was allowed to maintain spontaneous ventilation throughout general anesthesia for a thoracotomy. The patient was a 5-year-old boy complaining of productive cough and intermittent fever for 3 weeks. His chest radiograph and magnetic resonance imaging(MRI) film demonstrated a critically narrowed and deviated trachea at the level of the thoracic inlet to the proximal portion of the right bronchus. We can secure the airway by spontaneous ventilation without muscle relaxation and allowing the patient to breathe spontaneously and insertion of endotracheal tube distal to the narrowed portion of trachea.