목적: To evaluate the usefulness of costal cartilage as a graft material for mastoid cavity obliteration in preventingthe cavity problem after the canal wall down(CWD) mastoidectomy. 방법:The patients who underwent CWD mastoidectomy and mastoid obliteration with costal cartilage were enrolled. Operations were performed in 242patients from 2011 to 2014. Hearing results were checked according to the hearing result report guideline in chronic otitis media surgery of Korean Otologic Society. Postoperative complications were checked in the aspect of postoperative dehiscence, persistent otorrhea, ear drum perforation and absorption of mastoid obliteration material. 결과:Among 242 patients, 50(%) patients were diagnosed as Adhesive otitis media, 111(%) patients were cholesteatoma, and 81 patients were chronic otitis media. 32 patients and 75 patients underwent ossiculoplasty with TORP and PORP, respectively. 13 patients had tympanomastoidectomy type I and 44 patients had type III, while 7 patients were performed with cartilage columellization. 26 patients underwent tympanization and 45 patients were planned for 2nd stage operation.The mean duration of follow-up time was 14 months, with a range of 6-43 months. In the patients of mastoid obliteration with rib cartilage, the average air-bone gap(ABG) was 26dB preoperatively, which improved to 18dB postoperatively. The obliterated mastoid and middle ear aeration are well kept in postoperative computed tomography. 결론:Costal cartilage is an acceptable donor for mastoid obliteration in CWD mastoidectomy.