Learning Objectives: Learning objectives: In this study there was no association between fistula size on CT-scan and hearing level before cholesteatoma surgery. The type of fistulae found intraoperatively did not correspond to postoperative hearing. Introduction:To compare audiological results before and after surgery in subjects suffering from horizontal semicircular canal (HSC) fistulae due to cholesteatoma. To assess whether there was any relationship between 1) fistulae size according to preoperative CT-scan and pre-operative boneconduction hearing, and 2) type of fistulae found during surgery and post-operative bone-conduction hearing.Methods: Retrospective evaluation including 21adults suffering from cholesteatoma with preoperative CT-scan images. Intervention: open mastoidectomy with identification of HSC fistulae. Outcomes: to compare bone conduction thresholds before and after surgery and, to assess for correlation between 1) fistulae size on preoperative CT scan and preoperative bone conduction hearing loss, and 2) type of fistulae identified during surgery and postoperative bone conduction hearing loss. The study protocol was approved by the Ethical Committee on Clinical Research of our institution.Results: After surgery we detected a decline in bone conduction thresholds. We could not establish correlation between fistulae size on CT-scan and bone conduction hearing in the preoperative setting. Similarly, there was no correlation between fistulae type found during surgery and postoperative bone conduction hearing. Conclusions:In this series of subjects presenting with HSC fistulae due to cholesteatoma, we verified an increase in hearing loss after surgery. Correlation between fistula size on CT-scan and hearing level pior to surgery was not established. There was no correlation between the type of fistulae found during surgery and postoperative bone conduction hearing.