PURPOSE: CTAP(CT during arterial portography) has been shown to be the most sensitive technique available for the detection of hepatic mass. But because of many false positive lesions, it is important to interpretate the findings correctly. So we tried to analyse the false positive findings in CTAP. MATERIALS AND METHODS: Materials were 47 patients that had (;TAP for the detection of hepatic lesions. After performing superior roesenteric artery (SMA) arterial portography for the detection of vascular variation, CT^P was done. 100 to 150 cc of 50% diluted nonionic contrast media was injected at 2--3ml/sec rate. Spiral CT was used with 8mm slice thickness and 8mm/sec table speed. We compared the findings of CTAP with CTHA(CT during hepatic arteriography), enhanced (;T, anglogram, US, Lipiodol CT and biopsy. RESULTS: Twenty nine false positive lesions were found. There were 11 peritumoral defects, 7 straight line signs, 5 perihilar defects, 2 periligamentous defects, 3 subcapsular defects and 1 defect by cirrhosis. CONCLUSION: When CTAP is used for the evaluation of hepatic lesion(esp, preoperative evaluation), understanding of the false positive findings and the characterization of the lesion through multi-modality approaches are needed for the correct diagnosis and the proper treatment.