Postpneumonectomy syndrome is defined as an airway obstruction due to mediastinal shift and rotation after pneumonectomy. A patient who had undergone a left pneumonectomy for bronchial carcinoma 13 years before presented with tension pneumothorax of her remaining lung. Although all factors relevant to the development of postpneumonectomy syndrome were ascertained, the patient had a pneumothorax rather than an airway obstruction. This pneumothorax was treated surgically. The goal of this operation was to reduce the right pleural cavity volume by implanting an intrapleural prosthesis in the pneumonectomy cavity. This treatment is identical to that used for postpneumonectomy syndrome, which allows the right lung to be rejoined with the thoracic wall.