Breathlessness, along with the associated inability to engage in normal activity, is one of the most distressing symptoms for patients with chronic obstructive pulmonary disease (COPD). If treatment for breathlessness is started early in the disease, physical activity could, in theory, be improved or maintained; this may slow the progression of symptoms towards disability and improve quality of life. A significant cause of breathlessness in COPD is hyperinflation of the lungs due to air trapping, which occurs largely as a result of airflow limitation. Regular exercise reduces the respiratory demand of muscles and, by inference, the impact of air trapping during less intensive activities. Moreover, although airflow limitation in COPD is poorly responsive to anti-inflammatory drugs and less responsive to bronchodilators than in asthma, bronchodilators are clinically proven to bring perceivable symptom improvements in COPD. These improvements correlate with improvements in air trapping indices, which can be significant even in the absence of significant change in forced expiratory volume in 1 second (FEV(1)). The rationale for treatment in COPD, therefore, differs to that for asthma. Understanding of the pathophysiology of COPD improves our chances of achieving an effective intervention with the hope of a better quality of life for patients.