Many personal and environmental risk factors are associated to increased prevalence and severity of chronic obstructive pulmonary disease (COPD). In this review, we shortly describe most of these risk factors, aiming at defining each factor as causative or modifier of the natural history of the disease. It is clear that the environmental risk factors do have an outstanding relevance for both the initiation and the evolution of COPD. This review focuses on the crucial importance of prevention in order to decrease the public health burden of COPD in the western countries during the next decades.