PURPOSE: To compare the precise roles of high-resolution computed tomography (HRCT) and fiberoptic bronchoscopy (FOB) in the evaluation of patients presenting with hemoptysis and to determine the optimal timing for HRCT. MATERIALS AND METHODS: The results of HRCT and FOB were compared in 23 patients (15 men, 8 women) presenting with hemoptysis. Etiologies included bronchietasis (n=4), parenchymal pulmonary tuberculosis (n=4), lung cancer (n=4), endobronchial tuberculosis (n=2), and broncholithiasis (n=2). Hemoptysis was proved to be due to miscellaneous causes in an additional three cases and to be cryptogenic in four. The diagnostic results of FOB performed before and after HRCT were compared as were those of HRCT performed within and after the first 48 hours of active bleeding. RESULTS: FOB and HRCT offered a correct diagnosis in 39% and 65% of cases, respectively (p=0.005). HRCT demonstrated three cases of bronchiectasis and three of parenchymal pulmonary tuberculosis which were beyond the range of a bronchoscope. In two of five cases in which HRCT findings were nonspecific, chondromatous hamartoma and lung cancer were confirmed by FOB. In cases where HRCT was performed prior to FOB, the latter demonstrated the location and diagnosis in 82% and 47% of cases, respectively (p=0.303) ; when HRCT was performed after FOB, HRCT was correct in 67% and 17% of cases, respectively (p=0.178). In none of three cases (0%) in which HRCT was performed during the first 48 hours of active bleeding did the procedure allow a specific diagnosis. In 15 of 20 (75%) cases in which HRCT was performed after the first 48 hours, however, the diagnosis provided by CT was correct. CONCLUSION: The results of this study suggest that in patients presenting with hemoptysis, both HRCT and FOB should be used for evaluation, since they are diagnostically complementary. FOB is more useful for the diagnosis of endobronchial lesion, and HRCT for bronchiectasis and parenchymal pulmonary tuberculosis. If, in cases of hemoptysis, initial diagnosis is attempted within the first 48 hours of active bleeding, FOB should be the initial step, and HRCT images should not be obtained until active bleeding has been shown on plain chest radiograph to have abated. If this initial approach takes place after the first 48 hours of active bleeding, FOB and HRCT are equally suitable.