A 46-year-old woman with end-stage liver disease that was complicated by recurrent hepatic hydrothorax requiring multiple thoracenteses presented with breathlessness. Chest examination found no breath sounds on the right side. Radiography of the chest revealed a hydropneumothorax (Panel A; the arrows indicate pneumothorax, and the asterisk hydrothorax). The hydrothorax was drained with the use of a pigtail catheter, with persistent pneumothorax (Panel B, arrows). A computed tomographic scan of the chest showed trapped lung (pneumothorax ex vacuo) with thickened visceral pleura and no evidence of endobronchial obstruction (Panel C). Trapped lung is due to fibrous visceral pleural thickening from a chronic inflammatory process that prevents lung reexpansion. The noncompliant lung separates from the parietal pleura, and this space fills with fluid, with resultant hydropneumothorax. Drainage of the pleural fluid leads to pneumothorax ex vacuo because the lung cannot reexpand to fill the chest cavity. Once other causes of pneumothorax ex vacuo, such as endobronchial obstruction, are excluded, the management of trapped lung is surgical, with removal of the fibrosed visceral pleura to allow for the expansion of the underlying lung. In this patient, video-assisted thoracoscopic surgery with decortication and pleurodesis was performed, with complete reexpansion of the right lung.