We performed the operation for coronary artery-to-pulmonary artery fistula with aneurysm in two patients. The coronary angiograms of one patient, who was a 63-year-old female, revealed coronary artery-to-pulmonary artery fistula originated from the left coronary artery with 3 aneurysms of 2 cm in diameter, respectively. The angiogram of another patient, who was a 77-year-old female, revealed coronary artery-to-pulmonary artery fistula originated from both coronary arteries with the giant aneurysm of 7 cm in diameter. We decided to operate by the reason of possibility of rupture of the aneurysms, and performed resection of the fistulas and the aneurysms with the closure of the drainage openings into the pulmonary artery with the aid of cardiopulmonary bypass. It was recommended to resect the coronary aneurysm before growing big in the patient with the coronary artery-to-pulmonary artery fistula.