Paratracheal air cyst (PTAC) is rather frequently detected on thoracic multi-detector computed tomography (MDCT) in daily practice. Accessory cardiac bronchus (ACB) is a rare anomaly; however, the incidence rate is increasing with the use of recent high quality MDCT scanners. We report a case of combined PTAC and ACB that was incidentally detected by MDCT. Three dimensional CT images revealed anatomical details.