PURPOSE: To evaluate the hemodynamics of nodular hepatocellular carcinoma (HCC) using single-level dynamic CT during hepatic arteriography (CTHA) according to the size of the nodule. MATERIALS AND METHODS: Forty 40 patients with nodular HCC confirmed histologically or radiologically underwent single-level dynamic CTHA. Contrast media was injected via the hepatic artery for 20 seconds at a rate of 1.2 ml/sec. Images were obtained prior to this and thereafter at 3-second intervals until 30 seconds after the start of injection, and additional images at 45 and 60 seconds. The CTHA findings were retrospectively reviewed, and cases were assigned to one of three groups, according to the size of the tumor [<2 cm (group I, n=6); 2 -5 cm (group II, n=18); and > 5 cm (group III, n =16)]. We focused on onset time of contrast enhancement (CE), peak CE time and density, and duration of plateau. The patterns of CE were classified as homogeneous, heterogeneous, peripheral, or "nodule in nodule ". RESULTS: The onset time of CE was 3 seconds and mean peak CE time was 18.8 seconds. A plateau was noted in all groups (mean duration, 6.8 seconds). Mean peak CE time and density were 16.5 seconds and 294.1 HU in group I, 18.5 seconds and 324.1 HU in group II, and 20.1 seconds and 114.0 HU in group III. The most frequent pattern of CE (83%) was homogeneous, and this was found in group I. The small HCC group (group I) showed a faster mean peak CE time than the large group (group III) (p < 0.05), and this latter showed a lower peak CE density than the other groups (p < 0.05). In groups II and III, "nodule in nodule "(72%) and heterogeneous patterns (69%) were, respectively, the most frequent findings. CONCLUSION: Single-level dynamic CTHA is useful in evaluating the hemodynamics of HCC.