Demonstration of the fistulous tract linking pancreatic pseudocysts to the mediastinum and pleural cavity has diagnostic and therapeutic implications. In four cases, pseudocyst drainage through the esophageal and aortic diaphragmatic crus into the mediastinum and pleural cavity was delineated by computed tomography. In two cases, significant pericardial effusions were demonstrated. Computed tomography offers an effective diagnostic method when treatment is dependent on anatomic localization of the disrupted pseudocyst and its intrathoracic drainage tract.