PURPOSE: To describe the technical features of CT-guided percutaneous ethanol injection therapy (PEIT) for hepatic tumors that are undetectable or inaccessible under ultrasound guidance, to analyze its short-term therapeutic results, and to discuss its feasibility and limitations with a review of the related literature. MATERIALS AND METHODS: During a 22-month period, 17 patients with 28 hepatic tumors (27 hepatocellular carcinomas and one metastasis) underwent 38 sessions of CT-guided PEIT. Follow-up CT scanning was also performed. All tumors were undetectable or inaccessible under ultrasound guidance. The quantity of ethanol injected depended on their maximum diameter, which was 0.9 -5.1 (mean, 2.2) cm. To determine the puncture site and direction of the needle, the graduated grid system was used. A 21 or 22-G PEIT needle was introduced into the tumor stepwise, with intermittent CT monitoring, and if the CT images obtained immediately after initial injection demonstrated incomplete perfusion, an additional dose of ethanol was administered. During the follow-up period of 28 -619 (mean, 261) days, three-phase spiral CT scans were obtained. We focused on whether or not a viable portion of ablated tumor was present, and if so, the interval during which the extent of viable portion had changed, as well as the CT findings which suggested a predisposition to incomplete ablation. RESULTS: PEIT was successfully performed in all patients. During each session, 3 -30 (mean, 12.1) mL of ethanol was injected for 35 -115 (mean, 85) mins, with 1 -7 (mean, 3.7) trials to determine the puncture site and needle direction. The follow-up CT results showed that 20 tumors (71.4%) contained no viable portion, that this portion had decreased in four (14.3%), and was unchanged or had increased in four (14.3%). In the eight tumors for which multiple sessions were required, follow-up CT showed that the viable portion was absent or had decreased in size in all except one. In five of the patients with a tumor containing a viable portion at follow- up CT, the procedure was incomplete because of unendurable pain (n = 2) or noncooperation (n = 3). A CT finding which suggested a predisposition to incomplete ablation was a poor margin (n = 3). Complications included severe pain (n = 6) and scanty peritoneal hemorrhage (n = 1). CONCLUSION: Despite several limitations of our study, the therapeutic results of CT-guided PEIT appeared to be similar to or slightly worse than those of well-established ultrasound-guided PEIT with the former procedure, however, intermittent CT monitoring indicates whether perfusion is complete, and for this reason, CT-guided PEIT is believed to be an effective treatment modality when a hepatic tumor is undetectable or inaccessible under ultrasound guidance.