COPD is a major cause of morbidity and mortality. Its social and economic burden is expected to increase worldwide in coming decades. COPD is under-recognised and under-diagnosed. It results in disproportionately more numbers of physician visits, emergency department visits and hospitalisations than most other diagnoses. It is increasingly recognised that COPD is commonly accompanied by co-morbid medical conditions, cardiovascular disease, hypertension, diabetes, osteoporosis, chronic kidney disease, cognitive impairment and depression, due to systemic inflammation which impact on quality of life and survival. The prevalence of COPD among adults aged 40 and above varies widely from 8% to 26%. The most widely recognised risk factor for COPD is smoking, but non-smoking factors include biomass fuel, occupational exposure to dusts and gases, history of pulmonary tuberculosis, chronic asthma, respiratory-tract infections during childhood, outdoor air pollution, and poor socioeconomic status.