The most common causes of bronchiolitis obliterans organizing pneumonia ( BOOP) are connective tissue diseases, organ transplantation, drug reaction, and infections. Although rare, BOOP due to gastroesophageal reflux (GER) has been reported in adults but not to date in pediatric patients. This study describes 2 pediatric patients who developed GER and BOOP. One patient had superior mesenteric artery syndrome and Helicobacter pylori infection, and the other had a gastroduodenal ulcer with reflux esophagitis. Respiratory symptoms occurred concurrently or after gastrointestinal symptoms. Monitoring of esophageal pH for 24 hours revealed pathologic acid reflux. Lung biopsy findings confirmed BOOP. No other causes of BOOP were observed in these 2 patients. Both patients were cured with antireflux therapy and corticosteroids. To our knowledge, this is the first case report to implicate GER as a reversible cause of BOOP in children.