We evaluated radiological findings and clinical significance of right aortic arch with mirror-image branching (RAMI) in adults using data from computed tomography (CT) examinations.We reviewed recorded reports and CT images obtained from university and branch hospitals for RAMI in adults. The RAMI incidence in adults found on CT was assessed. Associated congenital and acquired cardiovascular diseases were evaluated.A total of 27 cases (14 men, 13 women; mean age, 59.4 ± 18.3 years) of RAMI were found. Among 107,014 cases in three hospitals, the RAMI incidence in the first, second, and third Tokai University hospitals were 0.018%, 0.012%, and 0.012%, respectively. Eight cases had high aortic arches and four cases had aortic diverticulum (AD) in proximal descending aorta. Three cases had a history of tetralogy of Fallot. One case with an absent left pulmonary artery and three cases with an aberrant left brachiocephalic vein were found incidentally. Two cases were associated with AD aneurysm and vascular ring formation. One case had stenosis of the left subclavian artery due to injury.Cases of RAMI found in CT examinations in adults were extremely rare. Some cases were associated with congenital anomalies and/or acquired cardiovascular disease.