Objective: To determine whether there is a difference in the prevalence of non-tumoral perfusion defects (NTPD) in left hepatic lobe during CT arterial portography (CTAP) through splenic (SA) and superior mesenteric artery (SMA) injection. Methods and patients: For the preoperative evaluation, 59 patients (20 females, 39 males) who either have colorectal carcinoma metastasis (n: 42) or hepatocellular carcinoma (n: 17) underwent CTAP examination. Patients were divided, into two groups (SA and SMA) according to the injection artery. The presence and type of NTPD in the left hepatic lobe were determined and compared. Results: There were significant differences in peripherally located wedge shaped, perihilar-periligamentous and pericholecystic NTPD, but no significant difference was found in lobar/segmental defects between the groups. Conclusions: Our study demonstrated lower prevalence of NTPD in the left hepatic lobe in CTAP's performed through SA injection and we think that this could be explained by the streamlining of portal blood flow. (C) 2003 Elsevier Ireland Ltd. All rights reserved.