목적: Canal wall down mastoidectomy with tympanoplasty as a surgical treatment of chronic otitis media has advantages of easy removal of the pathology and early detection of recurrence. However, this also has new discomforts not existed in canal wall up M&T. They inevitably come from a cavity in canal wall down M&T itself. Authors aim to introduce a canal wall down M&T methods to overcome a cavity problem. Furthermore, We evaluate the effectiveness of modified Palva flap in external auditory canal reconstruction and mastoid obliteration as a surgical treatment of chronic otitis media using postoperative hearing and temporal bone CT. 방법:We analyzed pure tone audiometry and temporal bone CT pre and postoperatively in 31 patients with chronic otitis media from Jan. 2013 to Jan. 2015. Air-bone gaps are used for hearing change with average decibels of 0.5KHz, 1KHz, 2KHz, 3KHz. Effectiveness of mastoid obliteration is evaluated with changes of external auditory canal volume, which is calculated pre and postoperatively on the temporal bone CT using ROI(region of interest) in PACS system. 결과:The patients consist of 10 males and 21 females with average age of 53.03 years old(23-75 years old). Among 31 patients, 24 patients are operated initially and remaining 7 patients received revision surgery as a initial operation. The ABG is 28.13dB preoperatively and 19.83dB postoperatively. The ratio of pre and postoperative EAC volume is 1.388. 1 patient suffered from postauricular infection postoperatively but cured soon with I&D and usual antibiotics. 결론:The modified Palva flaps used in this study are easy and effective methods in EAC reconstruction and mastoid obliteration. The hearings are improved and the status of mastoid obliteration are stable 1 year postoperatively.