Pulmonary arteriovenous fistula can occur in a variety of clinical situations including liver diseases, infections, metastatic carcinomas, systemic disorders, and after the palliation of congenital heart diseases. A 72-day-old male infant with Tetralogy of Fallot and pulmonary atresia underwent surgical correction without difficulty. However, ventilator weaning in the ICU failed initially because of an unexplained postoperative hypoxemia(FiO2: 0.8, PaO2: 40 mmHg, SaO2: 80∼90%). Postoperative follow-up lung perfusin scan at postoperative 15 days showed right-to-left shunt(33.6%) and ventilator weaning was performed on the 20th day after the operation (FiO2: 0.4, PaO2, 50mmHg, SaO2: 86.9%). Arterial oxygen saturation under room air was 80∼85% at 7 months postoperatively. One and half year follow-up lung perfusion scan showed decreased amount of right-to-left shunt (11.2%). We report a case with a review of the literatures.