In patients with suspected coronary artery disease (CAD), coexisting extracardiac abnormalities have a major impact on the patient management. This study aimed to evaluate the image quality of whole-body computed tomography (CT) immediately after the coronary computed tomography angiography (CTA) and investigate the incidence of extracardiac findings in patients with suspected CAD. We enrolled 450 patients undergoing whole-body CT at 100kVp and model-based iterative reconstruction immediately after the coronary CTA (Group A) and retrospectively reviewed 144 control patients who underwent conventional contrast-enhanced CT (120kVp) with filtered back projection (Group B). We compared the signal-to-noise ratio (SNR) of the aorta and liver and radiation dose between the two groups. Then, we evaluated the prevalence of extracardiac findings in Group A. Compared with Group B, Group A demonstrated significantly higher aorta and liver SNR and lower radiation dose. In Group A, whole-body CT revealed 229 coexisting lesions in 165 patients, including 32 and 106 cases of oncologic and vascular diseases, respectively. Additional whole-body CT after coronary CTA may provide adequate image quality. Using additional whole-body CT, 36% of patients with suspected CAD had clinically relevant coexisting findings, including malignancy.