Abrupt increase in the size of cervico-mediastinal tumor due to infection or spontaneous hemorrhage into cyst can induce severe tracheal compression and therefore sudden death. A 5 year old boy, who had a history of URI, had an enlarging cystic hygroma on the right side of the neck and anterior mediastinum. Under diagnosis of the cervico-mediastinal cystic hygroma, surgical removal was scheduled. After induction of anesthesia, intubation was done without any difficulty. A few minutes later, signs of partial airway obstruction were appeared. And within a very short period, total airway occlusion occurred. The tracheal tube was removed and manual ventilation was performed with positive airway pressure, but ineffective. We attempted to puncture cricothyroid membrane with 14 Gauge needle in order to ventilate manually. As soon as we puncture cricothyroid membrane, straw-colored fluid, not air, gushed out through a needle. After aspiration of about 200ml of cystic fluid, the obstructive signs disappeared and the patency of the airway was maintained. Intraoperatively, no more airway problems occured and vital signs were stable. And postoperatively, patient had no specific complications and discharged on the 7th day after operation.