We would like to present a case of persistent right sided collapse in a preterm baby with an unexpected diagnosis. Baby X was born floppy requiring resuscitation and was intubated, ventilated and was transferred to NICU. There was decreased air entry on auscultation of right side of the chest, while the rest of the examination was normal. The chest X-ray showed right side white-out suggestive of collapse consolidation. She required significantly high ventilatory pressures to maintain saturations and chest X-ray performed on day 4 remained unchanged with persistent right sided white-out. The CT scan of the chest showed no definable right lung, right pulmonary artery or right main bronchus. The diagnosis of right lung agenesis with single pulmonary artery was made and baby was found to have more congenital malformations on further investigations, and later developed complications leading to palliative care.