This study was aimed at evaluating the necessity to perform chest Computerized Tomography (CT) in multiple traumatized patients to diagnose pleuropulmonary lesions and, particularly, pneumothorax: the correct identification of this condition, although minimal, is important especially in prevision of long anesthesias and/or positive end-expiratory pressure (PEEP) therapy. This assisted respiratory technique improves arterial oxygenation but causes a barotrauma which may cause some complications; particularly, a small undetected pneumothorax can suddenly increase so as to cause pulmonary collapse with sometimes dramatic symptoms. Chest X-ray films and CT scans, performed in rapid succession on patient's admission in Emergency Ward, were compared in 21 subjects. CT is indispensable in case of severe chest parietal lesions which can mask the radiological evidence of pulmonary or pleural conditions, as it occurred in 3 of our cases. Moreover, CT resulted more reliable than chest X-rays (18 versus 10 correct diagnoses) especially in the detection of small antero-inferior pneumothorax flaps, in which direct radiological signs cannot be identified, in default of radio-geometrical assumptions. Indirect radiological signs of pneumothorax must be recognized but critically considered in order to avoid over-staging.