BACKGROUND: The accuracy of combined clinical examination (CE) and chest radiography (CXR) (CE + CXR) vs thoracic ultrasonography in the acute assessment of pneumothorax, hemothorax, and lung contusion in chest trauma patients is unknown. METHODS: We conducted a prospective, observational cohort study involving 119 adult patients admitted to the ED with thoracic trauma. Each patient, secured onto a vacuum mattress, underwent a subsequent thoracic CT scan after first receiving CE, CXR, and thoracic ultrasonography. The diagnostic performance of each method was also evaluated in a subgroup of 35 patients with hemodynamic and/or respiratory instability. RESULTS: Of the 237 lung fields included in the study, we observed 53 pneumothoraces, 35 hemothoraces, and 147 lung contusions, according to either thoracic CT scan or thoracic decompression if placed before the CT scan. The diagnostic performance of ultrasonography was higher than that of CE + CXR, as shown by their respective areas under the receiver operating characteristic curves (AUC-ROC): mean 0.75 (95% CI, 0.67-0.83) vs 0.62 (0.54-0.70) in pneumothorax cases and 0.73 (0.67-0.80) vs 0.66 (0.61-0.72) for lung contusions, respectively (all P < .05). In addition, the diagnostic performance of ultrasonography to detect pneumothorax was enhanced in the most severely injured patients: 0.86 (0.73-0.98) vs 0.70 (0.61-0.80) with CE + CXR. No difference between modalities was found for hemothorax. CONCLUSIONS: Thoracic ultrasonography as a bedside diagnostic modality is a better diagnostic test than CE and CXR in comparison with CT scanning when evaluating supine chest trauma patients in the emergency setting, particularly for diagnosing pneumothoraces and lung contusions.