Objectives - The aim of this study was to evaluate the variation of abdominal aortic diameter at L3 and T12 level in western UP population using CT abdomen, and to study the variation in abdominal aortic diameter with age and sex. Materials and Methods - In this study 131 both males and females were included with age 18 to 72. The patients without CVD (cardiovascular disease) and AAA (abdominal aortic aneurysm) underwent abdominal CT scans were recruited for this study. Routine protocol was used for abdomen CT scanning, the diameter of abdominal aorta measure in axial slice at the L3 level and T12 level in transverse and AP manner. Pearson correlation and t- test perform to evaluate correlation between aortic diameter, age and gender. Results -The mean and S.D. of transverse and AP diameter of abdominal aorta at L3 level in male patients were found as 15.0 ± 1.9 mm and 14.0 ± 1.7 mm respectively, while it found in female patients as 13.2 ± 1.6 mm and 13.0 ± 1.6 mm respectively. At T12 level it were analysed as 20.8 ± 2.8 mm and 20.9 ± 2.9 mm respectively while in female patients it found as 18.9 ± 2.6 mm 18.4 ± 2.5 mm. The mean and S.D. of the whole patients was 40.2 ± 15.0 years. The mean ± S.D. of transverse and AP diameter at L3 level were analysed as 14.2 ± 2.0 mm and 14.0 ± 1.9 mm respectively while at T12 level were analysed as 19.9 ± 2.9 mm and 19.8 ± 3.0 mm respectively. Conclusion - We observed in our study abdominal aortic diameter at L-3 and T-12 level in both planes transverse and AP significant correlate with age and gender. Male patients have aortic diameter greater than female patients. Abdominal aortic diameter increase with the age.