Interstitial lun g diseases (ILD), are a group of diseases which can involve pulmonary interstitium, small airways, and vessels, an d,diffuse ly affect pulmonary parenchyma as a conse q uence deve lo pment of inflammation, an d fib rosis lea din g to respiratory failure,an d fina lly death . Ob structive slee p a pnea s yn drome (OSAS) is adisorder wh ic h courses with its systemic outcomes, an d increasin gmorbidity, and mortality when accom panied with other respiratorysystem diseases. Concomitancy of OSAS with oth er lun g diseasesinclu din g c h ronic o b structive pulmonary disease, asth ma, ILD,cystic fib rosis is terme d asoverlap syn drome . Because of ch aracteristic feature of OSAS ie. recurrent oxygen desaturations during nigh t h ours, ILD-OSAS concomitancy accelerates progression ofunderlying lung disease. Th erefore, in cases with ILD, early diagnosis, an d treatment of comorbid OSAS conveys vita l importance inth at th is approach improves quality of life of th e patients, an d slows down progression of th e disease. In th is review ILD-OSAS con -comitancy will be analyzed from its various as pects .