PURPOSE: To evalvate whether in patients with diffuse evaluation of a hemidiaphragm on chest radiographs, the apparence of the crura on CT might be helpful in differentiating between traumatic rupture of the diaphragm(TRD) and nontraumatic causes such as diaphragmatic palsy or diffuse diaphragmatic eventration. MATERIALS AND METHODS: Among patients with diffuse elevations of a hemidiaphragm on chest radiograph, 27 who had patients undergone CT scans were retrospectively reviewed. Twelve patients had surgically proven TRD, and 15 had nontraumatic elevation of a hemidiaphragm such as diaphragmatic palsy or diffuse diaphragmatic eventration. Under the hypothesis that the affected crus is markedly thinner than the normal side in nontraumatic elevation but is normal in TRD ("crura sign"), we optically assessed without measurement the thickness of both crura. RESULTS: In all patients with TRD, the thickness of the affected crus was similar to that of the contralateral side. In all patients with nontraumatic causes, however, the crus of the elevated hemidiaphragm was markedly thinner than of the normal side. CONCLUSION: The "crura sign" may be useful additional CT finding of traumatic rupture the diaphragm.