| RDS (hyaline membrane disease) | prematurity, IDM, surfactant deficiency | low | diffuse fine reticulogranular ("ground glass"), air bronchograms, white‑out | rare | improves with surfactant; complications: PIE, pneumothorax, BPD |
| Transient tachypnoea (TTN, "wet lung") | term, caesarean, maternal diabetes/sedation | normal or high | streaky perihilar interstitial markings, fluid in fissures, small effusions | common | clears in 24–72 h |
| Meconium aspiration | term/post‑term, fetal distress | high (air trapping) | coarse patchy asymmetric opacities | sometimes | pneumothorax/pneumomediastinum common; PPHN |
| Neonatal pneumonia (GBS) | PROM, chorioamnionitis | variable | can mimic RDS (granular) | effusion favours pneumonia | antibiotics |
| Congenital diaphragmatic hernia | antenatal US often | ipsilateral small | bowel loops in the hemithorax, NG tube in chest, contralateral shift; Bochdalek (posterolateral, left ~85%) vs Morgagni (anteromedial, right) | — | pulmonary hypoplasia determines prognosis |
| Congenital lobar overinflation | LUL > RML | hyperlucent lobe | — | — | — |
| CPAM / sequestration | — | cystic/solid lesion; sequestration has a systemic arterial supply (aorta; CTA/Doppler) | — | — | — |