목적: To report the outcomes and associated factors of tympanoplasty type 1 alone and when combined with mastoidectomy. 방법:Consecutive patients with chronic otitis media who underwent tympanoplasty alone (T1 group, n=123) and tympanoplasty with mastoidectomy (TM group, n=52) by one surgeon were reviewed retrospectively. Mastoidectomy was performed when soft tissue density was observed in mastoid antrum on CT. Outcome measures were perforation closure and successful air-bone gap (ABG) 20 dB. The factors assessed were perforation site, perforation size, CT findings, and whether simultaneous mastoidectomy was performed. 결과:Overall, 159 (91%) of 175 cases showed successful ABG there was no difference between two groups. There was no difference in postoperative AC/BC pure-tone average (PTA) and preoperative BC PTA between two groups however, the preoperative ABG (207 dB) of TM group was significantly higher than that (148 dB) of T1 group (p<0.0001) and the improvement of ABG (99 dB) in TM group was higher than that (58 dB) in T1 group (p<0.001). In T1 group, small perforation showed significantly smaller preoperative ABG (97 dB) compared to those (157, 206, 239 dB) of moderate, large, and near-total perforations (p<0,01) and subsequently the former showed smaller postoperative improvement of ABG than the latters. Abnormal CT findings did not show any influence on hearing results. The postoperative re-perforation rate was 14% and most of them (15 of 21) were anterior pinpoint or small perforations. Deterioration of BC and AC PTAs > 15 dB after surgery was observed in 2% and 1%. 결론:Tympanoplasty type 1 showed high success rates (91%) regardless of simultaneous mastoidectomy. Patients who needed mastoidectomy showed higher preoperative ABG and could expect more hearing gain compared to tympanoplasty only group. Large and moderate perforations showed higher preoperative ABG and could expect more hearing gain compared to small perforation. Deterioration of BC after surgery was rare.