PURPOSE: To assess the diagnostic accuracy of dual-phase computed tomography during hepaticarteriography(CTHA) in depicting hypervascular hepatocellular carcinoma. MATERIALS AND METHODS: Forty patientswith hepatocellular carcinoma underwent dual-phase CTHA. First-phase data was obtained 6 seconds after contrastmedia was injected into the common hepatic artery, while second-phase data was obtained 35-40 seconds later.Lipiodol CT was performed 10-17 days after 2mL of lipiodol was injected into the proper hepatic artery. As agold-standard of 172 lipiodol-uptaken nodules seen on lipiodol CT, the detectability and positive predictive valueof the first and second phases, and the simultaneous interpretation of both phases, were analysed. RESULTS: Allnodules were detected by first-phase CTHA, 162 (94%) by second-phase CTHA, and 170 (99%) by simultaneousinterpretation of both phases. The detection sensitivities of first-phase CTHA and simultaneous interpretation ofboth phases were statistically superior to that of second-phase CTHA. Positive predictive values were 87% withfirst-phase CTHA, 96% with second-phase CTHA, and 97% with simultaneous interpretation of both phases. CONCLUSION: Dual-phase CTHA was useful for increasing detectability and accuracy in the diagnosis of hypervascularhepatocellular carcinoma.