COPD is the most frequent chronic lung disease in developed countries. Aim of our study was to assess prevalence of COPD in the population of one district of Warsaw. We studied 676 subjects, aged 41-72 years, (57% of the sampled representative population). Standardized questionnaire concerning history of lung diseases and smoking habits, physical examination and spirometry was taken in each subject. 13 subjects with asthma were excluded from further analysis. Symptoms of COPD and FEV1/FVC < 0.7 was found in 10.7% of the studied population. Tobacco smoking was the main risk factor. There was only a slight preponderance of the disease in males--53%. Extrapolating our data to a population of Poland it may be estimated that there are around 2,000,000 people affected by COPD. Whole nation epidemiological study on prevalence of COPD would be necessary to confirm that estimation.