COPD is usually caused by smoking and occasionally caused by other environmental exposures. It develops gradually over the years and will progress if smoking continues. There can also be coughing with sputum and episodes of lung infection. COPD can be associated with emphysema.

COPD and asthma can be difficult to distinguish in some people as symptoms can be similar. It is possible to have COPD and asthma. The diagnosis of COPD is sometimes suspected from the appearance of the chest x-ray but the chest x-ray itself cannot make the diagnosis of COPD. A breathing test called spirometry is essential in making the diagnosis of COPD and assessing its severity.

It is often important to carry out further assessments including measurement of blood oxygen, chest x-ray, CT scan, and blood investigations. These look for complications of COPD and help rule out other conditions.

Treatment can help alleviate breathlessness, improve the ability to exercise, and reduce infections in the lung.