Chronic obstructive pulmonary disease is mainly a smoking-related disorder and affects millions of people worldwide, with a large effect on individual patients and society as a whole. Although the disease becomes clinically apparent around the age of 40–50 years, its origins can begin very early in life. Different risk factors in very early life—ie, in utero and during early childhood—drive the development of clinically apparent chronic obstructive pulmonary disease in later life. In discussions of which risk factors drive chronic obstructive pulmonary disease, it is important to realise that the disease is very heterogeneous and at present is largely diagnosed by lung function only. In this Review, we will discuss the evidence for risk factors for the various phenotypes of chronic obstructive pulmonary disease during different stages of life.