Purpose: To evaluate the role of HRCT in the differentiation of pulmonary tuberculosis and lung cancer, where the manifestation of disease is a solitary pulmonary nodule(SPN). Material and Methods : Forty eight SPNsincluding 29 cancers proven by surgery(n=10), by bronchoscopic biopsy(n=7) and by fine needle aspiration biopsy(n=12), and 19 tuberculous nodules proven by surgery(n=4), by bronchoscopic biopsy(n=4), by fine needle aspiration biopsy(n=5), by a positive result in AFB culture without evidence of malignant cells(n=3), and by adecrease in size on serial plain chests despite negative AFB culture(n=3) were included. Scanning parameters forHRCT were 140KVp, 170mA, 1.5mm collimation, 3 sec scanning time, and a high spatial frequency algorithm was used. Results: With regard to the marginal features of nodules, the findings mor commonly observed in malignant nodules were greater average length of the longest spicule(5.35 $pm$ 3.19mm versus 2.75 $pm$ 1.56mm), and more commonspiculated nodules greater than 3cm in diameter, 16(55%) versus 2(10.5%)(P<0.05). Regarding the internal characteristics of nodules and perinodular parenchymal changes, the findings more commonly observed in cases of cancer were air-bronchograms within nodules(14;48.3%) and interlobar fissure puckering(6;20.7%), whereas intuberculosis cases the most common findings were low density of nodule(16;84.2%), cavitation(12;63.1%), and perinodular focal lung hypodensity(5;26.3%), (p<0.05). No statstically significant difference was observed between the incidence of satellite lesions of tuberculous(73.7%) and of malignant nodules(34.5%). However, perilobular nodules or bronchovascular bundle thickenings were more commonly observed in the satellite lesions of malignant nodules(9;90%), whereas centrilobular nodules or lobular consolidation were more commonly observed in those oftuberculous nodules(12;85.7%), (p<0.05). Conclusion: HRCT provides detailed information concerning perinodular parenchymal changes and characteristics of satellite nodules as well as marginal features and internal characteristics of SPNs which may play a significant role in differentiating pulmonary tuberculosis from malignant nodules.