Background: Lung hypoplasia, pulmonary persistent hypertension of the newborn and its morphological changes are the main features in congenital diaphragmatic hernia (CDH). This study was undertaken to investigate if antenatal use of sildenafi l and/or bosentan attenuates vascular remodeling, promotes branching, and improves alveolarization in experimental nitrofeninduced CDH. Methods: Nitrofen (100 mg) was gavage-fed to pregnant rats at post conception day (PCD) 9 to induce CDH. The rats were randomized to 5 groups: 1) control; 2) nitrofen; 3) nitrofen+sildenafil 100 mg/kg per day at PCD 16-20; 4) nitrofen+bosentan 30 mg/kg per day, at PCD 16-20, and 5) nitrofen+bosentan+sildenafil, same doses and administration days. After cesarean delivery, the offsprings were sacrifi ced. The diaphragmatic defect and pulmonary hypoplasia were identifi ed, and the lungs were dissected. Arterial wall thickness, bronchiolar density and alveolarization were assessed. Results: The offsprings with CDH were characterized by severe pulmonary hypoplasia (lung weight-to-body weight ratio: 0.0263 [95% confidence interval (CI) 0.0242-0.0278)] in the nitrofen group versus 0.0385 (95% CI 0.0355-0.0424) in the control group (P=0.0001). Pulmonary arterial wall thickness was decreased to 3.0 (95% CI 2.8-3.7) μm in the nitrofen+sildenafil group versus 5.0 (95% CI 4.1-4.9) μm in the nitrofen group (P=0.02). Terminal bronchioles increased to 13.7 (95% CI 10.7-15.2) μm in the nitrofen+bosentan group in contrast to 8.7 (95% CI 7.2-9.4) μm in the nitrofen group (P=0.002). More significant differences (P=0.0001) were seen in terminal bronchioles in the nitrofen+sildenafil+bosentan group than in the nitrofen group [14.0 (95% CI 12.5-15.4) μm versus 8.5 (95% CI 7.1-9.3) μm]. Pulmonary arterial wall thickness was also decreased in the former group. Conclusions: In this rat model, antenatal treatment with sildenafi l attenuates vascular remodeling. Bosentan promotes the development of terminal bronchioles in nitrofen-induced CDH.