The decision to repeat transcatheter arterial chemoembolization (TACE) for hepatocellular carcinoma (HCC) is based on correct evaluation of response to therapy. The purpose of this study was to investigate whether apparent diffusion coefficient (ADC), a quantitative parameter of diffusion-weighted imaging (DWI), can predict early HCC recurrence after TACE. Results obtained using this method were compared with those using iodized-oil computed tomography (CT). DWI was performed on 25 patients with 36 HCCs before and 5-7 days after TACE to calculate the ADC of HCC. Patients were also evaluated with iodized-oil CT immediately after TACE. Contrast-enhanced CT was performed 3 months after TACE to confirm early relapse of HCC lesion. After TACE, the percent change in ADC (%ADC) from before to after therapy was significantly increased in non-relapsed lesions (85.2+/-12.4%) compared to relapsed lesions (8.0+/-56.7%, p=0.0004). However, no difference in area under the curve was seen for receiver operating characteristic analysis to predict early relapse after TACE between %ADC from DWI (95% confidence interval, 0.743-1.026) and iodized-oil CT (95% confidence interval, 0.703-1.016). ADC from DWI can evaluate the efficacy of TACE for HCC as effectively as iodized-oil CT, and may help in deciding whether to repeat TACE.