PURPOSE: To determine the incidence of pseudolesions seen in the posterior aspect of segment IV of the liveron CT arterial portography(CTAP), and to evaluate the findings of CT hepatic arteriorgraphy(CTHA) and celiacangiography. MATERIALS AND METHODS: We retrospectively analysed 450 cases of patients who had undergone CTHA,CTAP and celiac arteriorgraphy for the diagnosis and treatment of hepatic lesion, and evaluated the incidence andimaging findings of pseudolesions in segment IV of the liver, as seen on CTAP, CTHA and celiac arteriography. RESULT: In 28 of 450 patients(6.2%), pseudolesions of focal perfusion defect were seen in segment IV on CTarterial portography. Pseudolesions were seen on CTAP on 39 different section slices ; these were wedge-shaped in41% of cases(16/39), rectangular in 30.8%(12/39), ovoid-shaped in 23.1%(9/39), and half moon-shaped in 5.1%(2/39); they were from 1 to 3cm(average, 1.5cm) in anteroposterior diameter, from 1 to 3cm(average, 1.9cm) in width, andfrom 1 to 4cm(average, 1.9cm) in craniocaudal diameter. Twenty-seven patients underwent CTHAs ; hyperattenuationwas seen in 13(48.2%), isoattenuation in 12(44.4%), and hypoattenuation in two(7.4%). In 19 of 28 celiacangiograms(67.9%), the right gastric artery was seen to arise from the hepatic artery, and aberrant right gastricveins directly draining into the left lobe of the liver were seen in three(10.7%). CONCLUSION: The incidence ofpseudolesion seen in segment IV of the liver on CTAP was 6.2% (28/450), and in 3 of 28 cases(10.7%), celiacangiography showed aberrant right gastric venous drainage. For pseudolesions, CTHA showed variable attenuation,and this modality is less sensitive than CTAP for the detection of pseudolesion.