A 36 year-old woman was subjected to resection of a giant thymoma that occupied a large area of the left hemithorax. After resection of the tumour and insufflation of the left lung there was pulmonary oedema due to early re-expansion. She was treated with diuretics and corticoids and was kept on mechanical ventilation. The patient progressed favourably. Although pulmonary oedema due to re-expansion is an uncommon complication it has a high mortality. It is essential to be aware of the factors involved in its aetiopathogenesis. It should be diagnosed and treated immediately.