PURPOSE: To compare the detectability of tumor vascularity using triphasic spiral CT, angiography, CT during hepatic arteriography(CTHA) and single-level dynamic CTHA(SLD-CTHA). MATERIALS AND METHODS: Seventy-nine pathologically confirmed nodular hepatocellular carcinomas(HCCs) in 77 patients were included in this study. Sixty patients were male and 17 were female, and their ages ranged from 31 to 77 (average, 57.4) years. HCCs were classified into three groups according to the size: less than 2 cm (n=20), 2 -4 cm (n=32), and more than 4 cm (n=27) in diameter. If a portion of tumor demonstrated greater enhancement than surrounding liver parenchyma, vascularity was deemed to be present. Detectability by each imaging technique was compared according to size and overall. RESULTS: Hypervascularity was frequently detected by SLD-CTHA [90.9%(40/44)], followed by CTHA[88.0%(66/75)], angiography [80.3%(61/76)], triphasic spiral CT [72.4%(42/58)]. In the less than 2 cm group, detectability rates for triphasic spiral CT, angiography, CTHA and SLD-CTHA were 53.3%(8/15), 55.6%(10/18), 76.5%(13/17) and 87.5%(6/7), respectively. while the 2 -4 cm group demonstrated corresponding figures of 71.4%(15/21), 78.1%(25/32), 84.4%(27/32) and 86.4%(19/22). In the more than 4 cm group, the rate for triphasic spiral CT was 86.4%(19/22), while for angiography, CTHA and dynamic CTHA, it was 100%. CONCLUSION: In the detection of hypervascularity of HCC, SLD-CTHA showed the highest rate, followed by CTHA, angiography, and triphasic spiral CT. In HCCs less than 4 cm in diameter, the corresponding ordering was SLD-CTHA, CTHA, angiography and triphasic spiral CT, but in HCCs of more than 4 cm, angiography, CTHA and SLD-CTHA detected hypervascularity equally well. Lesion size most affected the findings of angiography.