PURPOSE: To evaluate the enhancing patterns of nodular hepatocellular carcinomas (HCCs) in the arterial-andportal-dominant phases of spiral CT. MATERIALS AND METHODS: A retrospective analysis of enhancing patterns was performed in 100 patients with HCCs diagnosed by pathologic findings (n=30) or clinical and radiological findings. CT images were obtained 30 seconds(arterial-dominant phase) and 65 seconds(portal-dominant phase) after beginning injection of contrast medium (120mL, 3mL/sec). After transarterial chemoembolization, 179 tumors detected oniodized oil-CT were divided into four groups according to their largest diameter, as follows ; group I(smallerthan 1cm, n=51), II(1-2cm, n=46), III(2-3cm, n=32), IV(larger than 3cm, n=50). The enhancing patterns of tumorscompared with attenuation of surrounding liver parenchyma, were divided into four types, namely high, iso, low andmixed. RESULTS: Each group showed a different enhancing pattern ; group I showed iso-attenuation in both arterial- and portal-dominant phases (n=41, 80% and n=50, 98%), group II showed high-attenuation in the arterial-dominant phase (n=38, 83%) and iso-attenuation in the portal-dominant phase(n=34, 74%), group III showed high-attenuation in the arterial-dominant phase(n=19, 59%) and low-attenuation in the portal-dominant phase(n=17,53%), and group IV showed mixed-attenuation in both arterial- and portal-dominant phases(n=30, 60% and n=26, 52%). CONCLUSION: Hepatocellular carcinomas showed variable enhancing patterns on two-phase spiral CT according to thesize of tumors, and this reflected their hemodynamic characteristics.