Background: Validating non-contrast-enhanced computed tomography (nCT) compared to ultrasound sonography (US) as screening method for abdominal aortic aneurysm (AAA) screening. Methods: Consecutively attending men (n = 566) from the pilot study of the randomized Danish CardioVascular Screening trial (DANCAVAS trial), underwent nCT and US examination. Diameters were measured in outer-to-outer fashion. Sensitivity and specificity were done testing each modality against each other as reference standard. Measurements were tested for correlation, variance in diameters, and mean differences were tested using paired t-test. Results: Due to logistics, 533 underwent both nCT and US. In four patients, aortae could not be visualized with US, and two of these had an AAA (>30 mm) as diagnosed by nCT. Using nCT 30 (5.7%, 95% CI: 4.2;7.5%) AAA were found. US failed to detect 9 of these, but diagnosed 3 other cases, resulting prevalence by US was 4.5% (95% CI: 3.0;6.6%). Additionally, 5 isolated iliac aneurysms (≥20 mm) (0.9%, 95% CI: 0.3;2.2%) were discovered by nCT. US performed reasonably, with sensitivity ranging from 57.1-70.4%, specificity however, ranged higher 99.2-99.6%. Comparably nCT performed with sensitivity ranging from 82.6-88.9%, nCTs specificity however ranged from 97.7-98.4%. Analysis showed good correlations with no tendency to increasing variance with increasing diameter, and no significant differences between nCT and US with means varying slightly in both axis. Conclusions: nCT seems superior to US concerning sensitivity, and is able to detect aneurysmal lesions not detectable with US. Finally, the prevalence of AAA in Denmark seems to remain relatively high, in this small pilot study group.