Tension pneumocephalus is an uncommon complication of transsphenoidal surgery. This rare complication may be caused by an external lumbar subarachnoid drainage(ELD) which is placed for the treatment of a cerebrospinal fluid(CSF) fistula. Most of the tension pneumocephalus which cause severe neurologic deterioration in itself require surgical treatment. However, the pneumocephalus may be resolved after removal of the spinal subarachnoid catheter in some cases. We report two cases of tension pneumocephalus which developed after transsphenoidal surgery for the pituitary adenoma and craniopharyngioma, and fully recovered with conservative treatment.