Background. The concurrence of obstructive sleep apnea (OSA) and chronic obstructive pulmonary disease (COPD) is generally identified as an overlap syndrome. Only limited evidence is available on the prevalence of OSA in patients with stable COPD, and essentially no data on the prevalence of OSA in patients hospitalized for COPD exacerbation. The aims of the study were to determine the ratio of concurrence of OSA in patients hospitalized for COPD exacerbation and to identify the confounders of OSA detected in COPD subjects. Methods. 101 patients were hospitalized for COPD exacerbation at the Department of Respiratory Diseases in the course of four months. Seventy-nine consecutive patients were enrolled in the study and in 35 of these subjects polygraphy was performed. Descriptive statistics, Mann-Whitney test, Kruskal-Wallis test, Spearman correlation and Fisher's test were used to summarize and evaluate results. Results. In 18 (51.4%) subjects with polygraphy examination, the apnea–hypopnea index (AHI) >/= 5 indicated the presence of OSA. The AHI value, and thus the severity of the sleep disorder, correlated with the class of the Mallampati score, presence of snoring, apnea, coronary heart disease, diabetes mellitus in patient's history, height, body mass index, neck, waist and hip circumferences, and the value of the Epworth sleepiness scale. Conclusion. Polygraphy performed in patients hospitalized for exacerbation of COPD indicated an increased prevalence of OSA compared to the general population and stable COPD patients.