Capillary haemangioma presenting as a lung pseudocyst. A girl who developed a lung cyst at 24 hours of age during gentle ventilation for respiratory distress syndrome is reported. Instead of resolving as expected of a pseudocyst it continued to expand. Resection at 1 year of age showed a cyst entirely surrounded by capillary haemangioma. Aspiration of this cyst would have been dangerous. 