Prevalence of COPD is under-estimated, and more so among non-smokers. Population studies relying on spirometry show a trend toward higher proportion of persons with COPD who never smoked. In Switzerland, a third of subjects with airflow obstruction have never smoked. Subjects with asthma, bronchial hyperreactivity are more at risk. Exposure to passive smoking, indoor air pollution or biological dusts may cause COPD. This review discusses COPD prevalence in never smokers and details associated risk factors.