A century ago lung cancer was very rare – a clinical curiosity. Countries that then experienced the post-WW1 tobacco epidemic, saw sharp increases in lung cancer rates from the 1930s. Cases were in young smokers, mainly men and small cell lung cancer and squamous cell carcinoma predominated. Over time, with the evolution of the smoking epidemic, and changes in tobacco chemistry, lung cancer is seen in older people, more peripherally placed and many more cases of adenocarcinoma. This is the case in all countries with similar patterns of smoking trend to Australia. Other Western countries, lagging in smoking trends, lag in cancer trends as well. There are separate minor contributors including atmospheric pollution and occupational exposures on a background of variable genetic risk. Superimposed on this is the emergence of lung cancer in Asia, with different histology patterns and the superimposition of new genetic knowledge of lung cancer. Active smoking, environmental smoke exposure, domestic and outdoor air pollution on an uncertain background of possible genetic risk may jointly contribute to the different patterns of lung cancer we now see.