Chronic obstructive pulmonary disease (COPD) is a common disease worldwide with a high burden on healthcare resources. The prevalence of COPD varied from 11.4 to 26.1% according to a recent multi-city population study using spirometry. In Hong Kong (HK), the prevalence rates of COPD in the elderly population aged ≥60 years were 25.9% and 12.4% based on the spirometric definition of forced expiratory volume in 1s (FEV1)/forced vital capacity (FVC) ratio \<70% and the lower limit of normal of the FEV1/FVC respectively. In 2005, the crude mortality rate of COPD was 29.1/100 000, while the crude hospitalization rate was 193/100,000 in HK. In HK, COPD ranked second as a respiratory cause for hospitalization. In those 75 years or older, the hospitalization rate for COPD was as high as 2,225/100,000. The economic burden of COPD on the society is enormous. Previous studies gave information on the overall morbidity, mortality and the prevalence of COPD in HK. One study compared the management of COPD patients in HK with other countries and found that COPD patients in HK were under-treated. No large scale study has looked into the details of COPD patients in HK, like their co-morbidities and how they are being treated and how these factors affect the readmission of these patients. Large prospective studies which incorporate all the potentially relevant variables are required to refine prediction of the important outcomes of AECOPD and thus to inform clinical decision making, for example on escalation of care, facilitated discharge and provision of palliative care.