BACKGROUND AND OBJECTIVES: Multi-detector CT (MDCT) is becoming more commonly used as a diagnostic tool for various cardiac diseases, and this modality can also incidentally detect a significant number of non-cardiac findings during cardiac work-ups. The objectives of this study were to evaluate the incidence of non-cardiac findings during cardiac MDCT and to compare them with chest CT. SUBJECTS AND METHODS: We enrolled 1,007 consecutive subjects (mean age: 49+/-10 years, males: 63%) who underwent both cardiac and chest CT (64-slice MDCT) as a part of a routine health check-up. The subjects were evaluated for the incidence of non-cardiac findings and the therapeutic consequences according to the CT protocols during the mid-term follow-up (average length of mid-term follow-up: 533+/-39 days). RESULTS: Eight hundred sixty incidental non-cardiac findings were identified in 627 patients (62%) with cardiac CT. Forty-three subjects (4%) had clinically significant lesions that required additional diagnostic work-up or radiological follow-up, and these lesions were 23 cases of non-calcified nodule, 2 cases of ground glass opacity, 6 cases of pneumonia, 1 case of active tuberculosis, 2 cases of focal bronchiolitis, 3 cases of arterial lesion, 1 case of liver cirrhosis and 5 cases of extra-pulmonary masses. Five subjects (0.5%), including 2 cases (0.2%) of malignancy, had therapeutic consequences during their follow-up. Compared with chest CT, 68% (40/59) of the significant intrathoracic lesions and 67% (4/6) of the intrathoracic lesions with therapeutic consequences were documented by cardiac CT. CONCLUSION: In the present study, 4% of the asymptomatic patients who underwent cardiac MDCT were found to have significant non-cardiac findings that required further work-up. To avoid missing a number of clinically important findings, physicians who analyze cardiac MDCT scans should carefully evaluate not only the heart, but all the other organs that are within the scan range.