Negative pressure pulmonary edema (NPPE), or acute postobstructive pulmonary edema, is caused by negative intrathoracic pressure against an obstructed upper airway. Although NPPE is generally a benign condition, several fatal cases attributed to the delay in diagnosis have been reported. We report a case of NPPE experienced during Dumon stent placement. In a 39-year-old man, unilateral NPPE developed upon relief from a right main bronchial obstruction caused by a blood clot within the Dumon. The incident indicates that the "increased preload theory" is unable by itself to explain the pathophysiology of NPPE. Although we preferred spontaneous assisted ventilation for interventional rigid bronchoscopy, the potential risk of NPPE during Dumon stent placement, especially in spontaneously breathing young, healthy patients, needs to be considered.