PURPOSE: To evaluate contrast enhancement patterns of hepatomas (HCCs) on arterial dominant, portal dominant,and delayed phase of CT scan by using double spiral CT. MATERIALS AND METHODS: Using double-spiral CT, three-phase dynamic liver scan was performed on 27 patients with 45 nodular HCC lesions. Non-ionic contrast medium(100-120ml) was injected intravenously with an automatic injector at the rate of 2-4 ml/sec. CT scans were obtained at 25-30sec (arterial dominant phase), 60 sec (portal dominant phase), and 5min (delayed phase) afteradministration of the contrast medium. The tumor were divided into two groups according to the diameter(<3cm and > or = 3cm). In each group, contrast enhancement patterns of HCCs were classified as follows : high, central high, peripheral high, iso, low, or mixed attenuation. The incidence and contrast enhancement patterns of thin peripheral rims(psevdocapsules) were also analyzed. RESULTS: There were 23 lesions with a diameter less than 3cm,while 22 lesions were 3cm or larger. On the arterial dominant phase, tumors smaller than 3cm showed high(74%), iso(17%), mixed(4%), and peripheral high(4%) attenuation, while the attenuation of tumors larger than 3cm washigh(73%), mixed(9%), iso(9%), and low(9%). On the portal dominant phase, tumors smaller than 3cm were mostcommonly iso(43%) or high(35%), while tumors larger than 3cm were low(65%) or iso(18%). On the delayed phase, tumors were most commonly low in attenuation regardless of size. A thin peripheral rim was observed in 22% of tumors smaller than 3cm and in 64% of tumors larger than 3cm. The rim showed iso(53%) or low(42%) attenuation onthe arterial dominant phase, high(47%) or iso(47%) attenuation on the portal dominant phase, and high(100%) attenuation on the delayed phase. CONCLUSIONS: For the detection and diagnois of HCCS, an understanding of their contrast enhancement patterns is useful.