Re-expansion pulmonary oedema (RPO) is an uncommon clinical phenomenon encountered during the correction of chronic lung collapse. It has a mortality rate of 20%. Identification of the risk factors for RPO development may help in preventing the process. We presented an acute case of RPO complication which occurred within 3 hours following immediate water seal drainage of a right sided pneumothorax developed after the thoracotomy, and discussed the possible risk factors, mechanisms and preventive treatment options.