A case of pulmonary arteriovenous fistula in a 8-year-old boy who presented with easy fatigability and cyanosis for 4 months, is described. Grossly, there was a large vascular anomaly measuring 2x2 cm in the center of the removed right lower lobe. Microscopically, the lesion consisted of dilated arterial and venous structures resembling a cavernous hemangioma. Subintimal fibrosis and attenuated vascular structure lacking elastic fiber and representing A-V shunt were also noted in the lesion.