Lung cancer is the most frequent malignant tumour with the highest mortality rate around the world, leading to greater than a million deaths annually. The number of deaths due to lung cancer is expected to increase to ten million deaths per year in 2030. The major risk factor for the development of lung cancer is cigarette smoking but relatively high rates of lung cancer occur among non-smoking women and 10-25% of lung cancer observed in never smokers. The lung cancer deaths occur in never smokers have been estimated to be the 7th leading cause of cancer mortality. This article mainly discusses the important etiological factors of lung cancer in never smokers such as the environmental factors, occupational exposure, history of lung disease, family history and genetic factors, unbalanced diet and high consumption of saturated fat, radiation exposure, socioeconomic status, and infections. Gender, obesity and metabolic syndrome, race and ethnicity and interstitial lung diseases also have effects on the development of lung cancer in never smokers
