Lung cancer is a major cause of cancer deaths worldwide. The smoking epidemic remains the main risk factor accounting for 90 % of cases and the incidence of lung cancer has paralleled the adoption of smoking over time. In recent years, advances in understanding the genomics of lung cancer led to recognition of driver mutations in a proportion of patients and personalized approaches with targeted treatments have shown promising results in these subgroups. Although some trials in the last few years have suggested that screening programmes for high-risk populations can reduce mortality, prevention remains the most effective way to reduce lung cancer incidence and every effort should be directed towards smoking cessation programmes and public education. In this chapter, we will discuss the epidemiologic trends in lung cancer over time, the differences between populations and the effect of smoking and other environmental, occupational and host risk factors.