Chest radiographs and CT scans, obtained in six patients with proven postpneumonectomy empyema, were retrospectively reviewed by comparing the radiologic image obtained at present with that obtained before symptom onset. Convexity or straightening of the concave mediastinal margin of the postpneumonectomy space was identified on CT scans in all of six patients (100%), while contralateral mediastinal shift was noted on both radiographs and CT scans in four patients (67%). Multiple air-fluid levels appeared equally on radiographs and CT scans in three patients (50%). CT depicted increased thickening of the parietal pleura (n=5, 83%) and the extrapleural tissues (n=3, 50%) and empyema necessitans (n=2, 33%), which were not apparent on radiographs. Postpneumonectomy empyema is characterized on CT scans by reversal of the normal concavity of the mediastinal margin with increased thickening of the residual parietal pleura. CT is superior to radiography in assessing the manifestations of postpneumonectomy empyema.