According to the National Cancer Registry Programme, Mizoram has the highest cancer incidence among the states of India. Lung cancer has been found to be very common among the Mizos and its etiology has never been scientifically analyzed in this high cancer incidence population. A hospital based case-control study was conducted during March, 2014 to February, 2016. The study involved 106 histologically confirmed lung cancer patients and 212 matched cancer-free subjects acting as controls, all with the same ethnic background, i.e. Mizo. Among the cases, the risk of lung cancer was significantly elevated among ex-smokers (OR, 4.69; 95% CI, 2.36-9.32), but not among current smokers. Higher risks were seen for zozial smokers (OR, 2.51; 95% CI, 1.28-4.92). The increased risk was apparent among subjects who had smoked for ≥40 years. Exposure to environmental smoke at home and workplace were significantly associated with an increased risk of lung cancer. Higher risk was also observed for previous diagnosis of asthma (OR, 4.62; 95% CI, 1.75-12.23). Lower consumption of alcohol related with decreased risk of lung cancer (OR, 0.87; 95% CI, 0.37-2.05). Tobacco smoking was found to be the primary factor for developing lung cancer. Certain occupations like the transport industry, farming, carpentry or automobile works were found to increase the risk of lung cancer. Prior affliction with tuberculosis might also have the potential to increase the risk. However, low and moderate consumption of alcohol leads to decrease risk of lung cancer.