Objectives: This study aims to evaluate the clinical features of patientswho underwent surgery for isolated attic cholesteatoma and werediagnosed with selective dysventilation syndrome (SDVS).Patients and Methods: Pre- and postoperative clinical data of33 SDVS patients (20 males, 13 females; mean age 31.8 years;range, 17 to 56 years) operated on for isolated attic cholesteatomabetween January 2016 and September 2017 were retrospectivelyexamined and recorded. Mastoid development was evaluated frompreoperative temporal bone computed tomography images. Pre- andpostoperative first year pure tone audiometry test results were recorded.Based on intraoperative findings, patients were divided into threegroups according to epitympanic diaphragm/attic aeration pattern.The data of these three groups were compared statistically.Results: There were 17 type A (tympanic istmus blockage+completetensor fold), 10 type B (tympanic istmus blockage+attical verticalblockage+incomplete/complete tensor fold) and six type C (completeepidermization of the attic+complete tensor fold) patients. The mostcommon complaint in all groups was otorrhea. In groups A and B,mild retraction was generally observed in the tympanic membrane,whereas advanced retraction was observed in group C (p=0.002).There was evident mastoid hypopneumatization in each group andmastoid development was significantly worse in group C (p=0.023).In addition, facial dehiscence and recurrence rates were significantlyhigher in group C (p=0.006, p=0.011, respectively).Conclusion: Selective dysventilation in the epitympanum may causechronic middle ear diseases such as cholesteatoma behind mildretraction. The mastoid hypopneumatization caused by dysventilationis also undeniable in triggering this condition. During the surgery,particularly in isolated epitympanum pathologies, epitympanicdiaphragm should be carefully evaluated.