Chronic obstructive pulmonary disease or COPD is a name for a collection of lung diseases, most commonly emphysema and chronic bronchitis. This is one of the most common diseases of the respiratory system. It affects 6 % of the global population, almost equally men and women, and the prevalence increases with age. It is also the third leading cause of death throughout the world. The main cause of COPD is long-term exposure to irritating gases, most often from tobacco smoke. A number of other factors, such as air pollution, genetics or workplace dusts, chemicals and fumes, may also contribute to COPD. COPD develops slowly. Symptoms typically occur in people over the age of 40, although most people are not diagnosed until they are in their 50s. Symptoms include shortness of breath, persistent cough with sputum production, wheezing and frequent respiratory infections, primarily due to airflow obstruction, which is a result of inflammation and scarring within them. A sudden worsening of symptoms or acute exacerbation, commonly triggered by infection or environmental pollutants, is condition associated with increased shortness of breath, increased sputum production, or an increase in cough. Consequently, this can lead to insufficient ventilation and cause the changes which may result with cor pulmonale. COPD is diagnosed by history, clinical examination and spirometry, which is the gold standard in diagnostic procedure. The treatment involves quitting smoking, vaccinations, respiratory rehabilitation and medications, most often inhaled bronchodilators and steroids. Some patients require long-term oxygen therapy and lung transplantation. Although this treatment will not cure the patients, it may delay the progression of COPD.