PURPOSE: To predict the therapeutic efficacy of transcatheter oily chemoembolization(TOCE) in the treatment. MATERIALS AND METHODS: We reviewed the findings of 24 dynamic CT or MR scans examined for the purpose of diagnosis before TOCE, and follow-up CT scans obtained after this procedure. In 24 patients (M:F=20:4) with a mean age of 52.2 years, 43 nodular HCCs with a diameter of 5 cm or less were present. The patients underwent double dynamic CT or MR imaging as one arterial phase 30 seconds after the intravenous injection of contrast media, and this was followed by a delayed phase 5 minutes fter injection. HCCs were then classified as one of four types: Type I, high and low attenuation or intensity during the arterial and delayed phase, respectively; Type II, iso- and low; Type III, iso- and high; and Type IV, high and iso-. In addition, we classified the degree of lipiodol accumulation by HCC nodules as either Grade 5 (fullmoon-like lipiodolization), Grade 2 (about 40%), or Grade 1 (about 20%), as seen on follow-up CT scans after TOCE. RESULTS: Type I provided an accuracy of 72.1% considering to more than 50% lipiodol accumulation. However, a single finding demonstrating high atenuation or intensity during the arterial phase gave an accuracy of 79.1% better than that of Type I. CONCLUSION: A finding of high attenuation or intensity during the arterial phase, as seen on dynamic CT or MR images, provides the best information about the therapeutic efficacy of HCCs treated by means of with TOCE.