We report two cases of pulmonary collapse that simulated pneumothorax on computed tomographic images and were caused by rapid complete bronchial obstruction. One patient was a 77-year-old woman with sudden dyspnea, and the other was an 83-year-old woman with sudden dyspnea who was infected with influenza A virus. Chest computed tomography revealed lobular complete atelectasis with an almost complete expansion of the other lobes of the right lung. Some air space in the right pleural cavity was also observed. Both cases were diagnosed as "pneumothorax" by primary doctors. We noted the disappearance of air density in the lumen of the right bronchus in both cases. We performed bronchoscopy before thoracic drainage and removed the obstruction. Immediately, the obstructed pulmonary lobes expanded, and the air space in the pleural cavity disappeared without thoracic drainage. In the literature, this pneumothorax-like pulmonary collapse is called as "pneumothorax ex vacuo."