This report describes anesthetic management of a case (a 64-year-old man) who was originally diagnosed as paraesophageal hernia before surgery and later diagnosed as Bochdalek hernia during laparoscopic surgery. Anesthesia was started with oxygen, nitrous oxide, and sevoflurane, and respiration was managed using controlled mechanical ven-tilation. Although left pneumothorax was noticed during laparoscopic surgery (aeroperitonia pressure: 10cmH2O), the surgery was performed using the same anesthesia procedure, because hardly any changes were observed on the monitor and vital signs were stable. The surgery was completed without incident. However, postoperative chest X-rays revealed the residual large pneumothorax. A chest drain tube was inserted immediately, after which the pneumothorax was improved. Pneumothorax is considered to be inevitable in cases of laparoscopic repair of Bochdalek hernia. To prevent exacerbation of pneumothorax, anesthetic management should consist of discontinuing the use of nitrous oxide and lowering the aeroperitonia pressure concomitently with the use of positive airway pressure. © JSA 2005.