Introduction:This study aims to describe the occurrence of postoperative complications related to cholesteatoma surgery and to determine factors influencing the most common complication,i.e.post-operative surgical site infection (SSI) in cases with and without mastoid obliteration.Materials and methods:Retrospective analyses were performed on surgically treated cholesteatomas in our hospital between 2013 and 2019.Patient characteristics,peri-and postoperative management and complications were reviewed.The cases were divided into two groups based on whether mastoid obliteration was performed or not.Results:A total of 336 cholesteatoma operations were performed,of which 248 cases received mastoid obliteration.In total 21 complications were observed,of which SSI was the most common (15/21).No difference in occurrence of any postoperative complication was seen between the obliteration and no-obliteration group (p =0.798),especially not in the number of SSI (p =0.520).Perioperative and/or postoperative prophylactic antibiotics were not associated to the development of an SSI in both groups.In the no-obliteration group a younger age (p =0.015),as well as primary surgery (p =0.022) increased the risk for SSI.In the obliteration group the use of bioactive glass (BAG) S53P4 was identified as in-dependent predictor of SSI (p =0.008,OR 5.940).Discussion:SSI is the most common postoperative complication in cholesteatoma surgery.The causes of SSI are multifactorial,therefore further prospective research is needed to answer which factors can prevent the development of an SSI in cholesteatoma surgery.