Background <p>It is well known that there is increased prevalence of sleep breathing disorders (SBD) among COPD patients.Therefore, it is of important to study the risk factors associated with sleep breathing disorders in different degrees of severity in COPD patients.</p> Aim of the work <p>To assess different medical and functional risk factors associated with sleep breathing disorders in COPD patients with different functional impairment.</p> Patient &amp; method <p>The study is a cross sectional study which was carried at Chest Department in Beni-Suef University Hospitals about 50 stable COPD patients. All cases were admitted in the Chest Department and underwent the following:</p> <p>History taking, and examination was done, BMI calculations, arterial blood gases analysis, pulmonary function tests, unattended polysomnography that was conducted in the sleep lab unit.</p> Results <p>Among the 50 cases studied, the mean age in the COPD group was 61.6 ± 8.5..thirty-five of them having AHI &gt; 5 with 94% with obstructed apnea .38% had severe degree of obstruction, versus 36% had very severe degree and 26% had a moderate degree of obstruction. As regards mMRC 54% had a mild degree, 30% show moderate degree, and 16% had a severe degree. very severe obstructed COPD cases had a significant higher mean of severe AHI index (38.9%) there was a statistical significant lower mean value of FEV1/FVC, FEV1, 6MWT and a higher mean of ESS, and Stop Bang questionnaire among cases with sever degree of AHI. We found a positive correlation between AHI and each of FVC, Stop Bang questionnaire, and Epworth Sleepiness Scale but negative correlation with FEV1/FVC, FEV1, and 6MWT. On the other hand, we did not find a significant correlation with age, BMI, neck circumference, or FEF25/75.</p> Conclusion <p>In COPD patients increasing in the impairment of FEV1 &amp; 6MWT increasing the incidence of SDB.</p>