PURPOSE: To assess the value of adding a reformatted computed tomography (CT) rib series to transversely reconstructed CT imaging in the evaluation of rib fractures in patients with suspected traumatic thoracic injuries. MATERIALS AND METHODS: One hundred consecutive patients with suspected traumatic thoracic injuries underwent 128-section multi-detector row CT. Transverse CT images with 5-mm-thick sections were reconstructed and rib series were reformatted using isotropic voxel data. Three independent radiologists, who were blinded to the data, interpreted the CT scans at 2 sessions with a 4-week interval between the sessions. Only transverse CT images were reviewed at the first session. At the second session, the CT images were reviewed along with the reformatted CT rib series. The following parameters were analyzed: receiver operating characteristic (ROC) curve, pairwise comparisons of ROC curves, sensitivity, specificity, positive predictive value, and negative predictive value. RESULTS: There were 153 rib fractures in 29 patients. The level of the area under the ROC curve, Az improved for all observers. The diagnostic sensitivity and specificity of each observer tended to improve in the second session. The mean confidence scores for all observers of patients with rib fractures improved significantly in the second session. CONCLUSION: A reformatted CT rib series together with transverse CT scan is useful for the evaluation of rib fracture.