The association between atherosclerosis in the descending thoracic aorta (DTA) visualized on computed tomography coronary angiography (CTA) and coronary artery disease (CAD) has not been extensively explored. Therefore, a comprehensive analysis of DTA atherosclerosis on CTA was performed and the association of DTA atherosclerosis with CAD was evaluated in patients with suspected CAD. A total of 344 patients (54 ± 12 years, 54% men) with suspected CAD underwent CTA. CTA were classified based on CAD severity in no signs of atherosclerosis or minor wall-irregularities <30%, non-significant CAD 30-50%, or significant CAD ≥50% stenosis. The DTA was divided in segments according the posterior intercostal arteries. Per segment the presence of atherosclerotic plaque (defined as ≥2 mm wall thickness) was determined and maximal wall thickness was measured. Plaque composition was scored as non-calcified or mixed and the percentage of DTA segments with atherosclerosis was calculated. Significant CAD was present in 152 (44%) patients and 278 (81%) had DTA atherosclerotic plaque. DTA maximal wall thickness and percentage of DTA segments with atherosclerosis were 2.7 ± 1 mm and 49 ± 36%. The presence, severity and extent of DTA atherosclerosis significantly increased with increasing CAD severity. Multivariate logistic regression analysis corrected for age and other risk factors demonstrated independent associations of DTA plaque (OR 6.56, 95% CI 1.78-24.19, p = 0.005) and maximal DTA wall thickness (OR 2.00, 95% CI 1.28-3.12, p = 0.002) with significant CAD. The presence and severity of DTA atherosclerosis were independently related with significant CAD on CTA in patients with suspected CAD.