Neonatal bile acid pneumonia (NBAP) occurs in neonates following obstetric cholestasis. We aimed to study the lung aeration and respiratory support of NBAP. Nested, case/control study enrolling age-matched neonates with NBAP, respiratory distress syndrome (RDS) or transient tachypnoea (TTN). Lung aeration and oxygenation were assessed with lung ultrasound score, oxygenation index and SpO2 /FiO2 . Nineteen, 22 and 25 neonates with NBAP, RDS and TTN, respectively were studied (mean gestational age 33 (2.2) weeks, 30 (45.5%) males). Upon admission, RDS patients had worst lung ultrasound score (p=0.022) and oxygenation index (p=0.001), while NBAP and TTN neonates had similar values. At the worst time-point, NBAP and RDS patients showed similar oxygenation index (NBAP: 4.6 (2), RDS: 5.7 (3)) and SpO2 /FiO2 (NBAP: 3.1 (1.1), RDS: 2.7 (1)) which were worse than those of TTN patients (oxygenation index: p=0.015, SpO2 /FiO2 : p=0.001). RDS neonates needed the longest continuous positive airway pressure and highest mean airway pressure, but NBAP neonates needed invasive ventilation (26.3%, p=0.01) and surfactant (31.6%, p=0.003) more often than TTN patients who never needed these. NBAP was a mild disorder in the first hours of life but subsequently worsened and became similar to RDS.