Hydrothorax of the cerebrospinal fluid after a subarachnoid-pleural fistula is a rare condition. Subarachnoid-pleural fistula may appear after a trauma at the thoracolumbar vertebral column or iatrogenically after thoracotomy. A two years and four months old boy who was operated because of ganglioneuroblastoma was admitted to hospital due to respiratory distress. The chest roentgenogram obtained two months after thoracotomy, showed a pleural effusion at the left side and a chest tube was inserted. The craniospinal magnetic resonance imagining revealed subarachnoid-pleural fistula and lumbar external cerebrospinal fluid drainage was performed. The chest tube was removed by application of tetracycline between pleural layers. After the patient was discharged, respiratory distress reoccured after 3 weeks and a chest tube was reinserted due to fluid at the left hemithorax. An external lumbar drainage was reapplied. The location of the fistula was determined by craniospinal magnetic resonance imagining and myelography. The fistula was surgically restored by a posterior approach and laminectomy. The cerebrospinal fluid drainage and chest tube was removed three days and seven days after the operation respectively. The patient was discharged at the 13 days after the operation. During periodical outpatient follow up the patient has no symptoms and is neurologically intact. Subarachnoid-pleural fistulas, usually do not regress spontaneously or respond to conservative methods. Invasive approaches including surgery may be needed to treat patients with subarachnoid-pleural fistulae.