Background <p>Lower thoracic vertebral attenuation measured on coronary artery calcium scoring images may provide an opportunistic computed tomography-based bone health indicator (CT-BHI). This study evaluated the association of CT-BHI with coronary artery disease (CAD) severity and all-cause mortality.</p> Methods <p>We retrospectively analyzed 767 patients with suspected CAD who underwent coronary CT angiography (CCTA) and coronary calcium scoring. Individuals with prior myocardial infarction or revascularization were excluded. CT attenuation was measured in two lower thoracic vertebrae on calcium scoring images, and their mean value was defined as CT-BHI. Patients were categorized into tertiles by CT-BHI (higher, intermediate, lower).</p> Results <p>The lower CT-BHI group had significantly higher calcium scores (median [IQR]: 146 [4–548]) than the higher (25 [0–277]) and intermediate (39 [0–269]) groups (<i>p</i> &lt; 0.001). CCTA findings revealed a significant difference in CAD severity distribution among the three groups (<i>p</i> = 0.037), with the low CT-BHI group exhibiting a lower prevalence of normal coronary arteries. Combining low CT-BHI with high calcium score enhanced risk stratification (<i>p</i> &lt; 0.05). In multivariate Cox analysis, CT-BHI remained an independent predictor of mortality after adjustment for calcium score (<i>p</i> &lt; 0.05). Adding CT-BHI to calcium scores significantly improved risk classification (continuous net reclassification improvement, 0.263; <i>p</i> = 0.041).</p> Conclusions <p>CT-BHI derived from routine calcium scoring images may provide a dual-purpose opportunistic marker for integrated cardiovascular and skeletal risk assessment without additional radiation exposure or cost. Further studies are warranted to validate CT-BHI against standardized bone density measurements and determine its role in improving clinical management.</p> Clinical trial number <p>Not applicable.</p>