<b><i>Objective:</i></b> To correlate prenatal indicators of pulmonary hypoplasia with neonatal lung function and pulmonary hypertension (PHT) in isolated congenital diaphragmatic hernia (iCDH). <b><i>Materials and Methods:</i></b> Prospective single-center study on 40 fetuses with iCDH either expectantly managed (n = 13) or undergoing tracheal occlusion (n = 27). Prenatal predictors included observed/expected lung-head ratio (O/E LHR), observed/expected total fetal lung volume, fetal pulmonary reactivity to maternal O₂ administration (&#x0394;pulsatility index, &#x0394;PI) and liver-to-thorax ratio (LiTR) as measured in the second and third trimesters. Postnatal outcome measures included survival until discharge, best oxygenation index (OI) and alveolar-arterial oxygen gradient [D(A-a)O₂] in the first 24 h of life and the occurrence of PHT in the first 28 days of life. <b><i>Results:</i></b> Median gestational age (GA) at evaluations was 27.2 and 34.3 weeks. GA at delivery was 36.0 weeks, and overall survival was 55%. In the second trimester, measurement of lung size, LiTR and pulmonary reactivity were significantly related to survival and the best OI and D(A-a)O₂.The occurrence of PHT was better predicted by &#x0394;PI and LiTR. <b><i>Conclusions:</i></b> O/E LHR, LiTR and vascular reactivity correlate with ventilatory parameters in the first 24 h of life. Occurrence of PHT at ≥28 days was best predicted by LiTR and &#x0394;PI, but not by lung size.