Objective To investigate the application value of CT angiography (CTA) in the diagnosis of moyamoya disease in adults. Methods A total of 45 adults with suspected moyamoya disease treated in our hospital during the period from March 2013 to January 2017 were enrolled in this study. All patients underwent head and neck CTA after admission. The CTA imaging findings of adults with moyamoya disease were observed with the results of cerebral digital subtraction angiography (DSA) as the golden standard. The value of CTA in the diagnosis of moyamoya disease in adults was evaluated. Results Results of CTA showed that there were different degrees of vascular stenosis in 10 cases, hemorrhagic symptoms in 15 cases and ischemic symptoms in 20 cases among the 45 patients. Ends of the both sides of the internal carotid artery were obviously involved in 20 cases, the left side was involved in 18 cases and the right side was involved in 7 cases. There were 5 cases with vertebrobasilar stenosis, 21 cases with compensatory dilatation and 19 cases without obvious changes. With DSA as the golden standard, the sensitivity, specificity, accuracy and kappa consistency of CTA in the diagnosis of moyamoya disease were 90.00% (27/30), 86.67% (13/15), 88.89% (40/45) and 0.754 respectively. There was no significant difference of scores CTA and DSA in the diagnosis of vascular stenosis in adult moyamoya disease (P>0.05). Conclusion CTA has high diagnostic efficacy in adults with moyamoya disease, and it can accurately assess the degree of stenosis of cerebral vessels in patients.