To assess the risk of cancer incidence after medical radiation exposure for coronary artery disease (CAD),a retrospective cohort study was conducted based on Taiwan’s National Health Insurance Research Database(NHIRD). Patients with CAD were identified according to the International Classification of Diseases code, 9thRevision, Clinical Modification (ICD-9-CM), and their records of medical radiation procedures were collectedfrom 1997 to 2010. A total of 18,697 subjects with radiation exposure from cardiac imaging or therapeuticprocedures for CAD were enrolled, and 19,109 subjects receiving cardiac diagnostic procedures withoutradiation were adopted as the control group. The distributions of age and gender were similar between thetwo populations. Cancer risks were evaluated by age-adjusted incidence rate ratio (aIRR) and association withcumulative exposure were further evaluated with relative risks by Poisson regression analysis. A total of 954and 885 subjects with various types of cancers in both cohorts after following up for over 10 years were found,with incidences of 409.8 and 388.0 per 100,000 person-years, respectively. The risk of breast cancer (aIRR=1.85,95% confidence interval: 1.14-3.00) was significantly elevated in the exposed female subjects, but no significantcancer risk was found in the exposed males. In addition, cancer risks of the breast and lung were increased withthe exposure level. The study suggests that radiation exposure from cardiac imaging or therapeutic proceduresfor CAD may be associated with the increased risk of breast and lung cancers in CAD patients.