['High lung cancer mortality is observed among female never-smokers in Hong Kong.', 'To examine the relationship between obstructive lung disease (chronic obstructive pulmonary disease and/or asthma) and lung cancer mortality by sex and smoking status.', 'A cohort of elderly clients (aged ≥65 years) in a health maintenance programme were followed prospectively through linkage with the territory-wide death registry for causes of death, using identity card number as the unique identifier.', 'After 516,055 person-years of follow-up, respectively 1297, 872 and 1908 deaths were caused by lung cancer, other tobacco-related malignancies and non-tobacco-related malignancies. In the overall analysis, obstructive lung disease was independently associated with mortality due to lung cancer (aHR 1.86, P < 0.001) after adjustment for potential confounders. However, no association was detected among female never-smokers (HR 0.97, P = 0.909), in sharp contrast with female ever-smokers, male never-smokers and male ever-smokers (HR 1.98, 2.34 and 2.09, respectively, P from 0.047 to <0.001). Consistent results were observed after exclusion of all deaths in the initial 3 years.'] Does obstructive lung disease increase lung cancer mortality among female never-smokers in Hong Kong?