Computerized tomography (CT) of the chest is now widely used in pneumological practice. It has completely superseded conventional tomography and reduced the number of bronchographies and pulmonary angiographies. CT is superior to conventional examinations in detecting lymph node enlargements, solid tumours, granulomas, fat deposits, calcifications, pulmonary necrosis and pleural plaques and in demonstrating tumoral limits. In the lung itself, the information provided by CT is of subsegmental accuracy. The new method is capable of diagnosing bronchiectasis and emphysema and evaluating their extension; it also gives a good visualization of chronic interstitial lung lesions.