Abstract: The purpose of this study is to examine the accuracy of a 3D simulation generated by inclusion of various intensity-selected portions of spiral CT data into a proprietary software program (PreviewTM, Medical Media Systems, MMS) in preoperative and postoperative assessment of the anatomical features of abdominal aortic aneurysm (AAA). The accuracy of this software was measured against two other modalities—intravascular ultrasound (IVUS) and axial CT scan—using the IVUS as the reference. Eighty-five patients were included; 43 underwent AAA endovascular exclusion with TalentTM devices, and 42 with AneurxTM devices. Measurement of proximal neck diameter was performed using IVUS, Preview software, and axial CT scan with manual calipers. Measurement of the AAA maximum diameter was performed using Preview software and axial CT scan; 253 measurements in the 85 patients were included. These measurements were compared by means of both linear regression and Bland-Altman agreement analysis. Our results showed that the 95% confidence interval between the Preview software and mean IVUS measurement of proximal AAA neck (3.1 and 2.5) is narrow enough for the software to be used in sizing AAA. This would be especially important for having the properly sized devices available preoperatively. The Preview software tended to be more accurate than CT scans although it was not statistically significant.