Emphysematous cystitis is a rare condition characterized by gas collection in the wall and lumen of the bladder. We experienced three cases of emphysematous cystiris. All patients were female; one was associated with a long term history of diabetes mellitus and another with urinary indwelling catheter. All of the cases were easily diagnosed on plain radiograph and CT scan, and were successfully treated with antibiotic therapy. In one of the cases, however, associated abscess due to perivesical extension of inflammation was treated by combined external drainage.