In our study we aimed to examine the sleep structure, oxygenation and breathing pattern in interstitial lung disease (ILD) patients. We also aimed to determine whether relevance between the advanced disease and the sleep disorders exists and whether polysomnography is necessary in those patients. A total of 37 patients were examined in the study and whole night standard polysomnography was performed to all. Polysomnography results revealed that, total sleep time, time spent in NREM sleep stage III and IV, and in REM sleep were decreased. The patients had poor sleep efficiency and they spent more time as wake after sleep onset (WASO). Severe oxygen desaturations were detected during sleep and statistically significant positive correlations were found between mean awake O2 saturation and mean and lowest sleep O2 saturations. Clinical, Radiological and Physiological (CRP) scoring system was used to assess the disease stage, whether advanced or not, and statistically significant negative correlations were found between CRP score and awake and sleep O2 saturations. Obstructive sleep apnea syndrome (OSAS) was diagnosed in 24 (64.9%) patients. In those patients it was found that not the apneas but the hypopneas predominate. No difference was found among body mass indices (BMI) between the patients with and without OSAS. As a result it was concluded that a sleep study should be considered as part of the overall assessment in managing patients with ILD, and is especially indicated if there is incipient pulmonary hypertension, cor pulmonale and nocturnal arrhythmia despite normal awake blood gas tensions and symptoms as snoring and excessive day time sleepiness.