Lung cancer is a leading cause of death with changing trends of occurrence, detection and treatment. The objective of this research was to identify impact of risk factors on changing trends of lung cancer in a case control study. In the study conducted from 2006 to 2010 the cases included newly diagnosed patients of histological proven lung carcinoma attending the radiotherapy department. For each case, one control was identified and matched with same sex, age ± 5 years, and unmatched for residence, smoking status and socioeconomic condition. For categorical variables, Chi Square and Fisher’ test and for numerical variables t test and Mann Whitney tests were used. All univariate analyses used ANOVA test. Variables with p < 0•05 were entered in Cox proportional hazards regression model. During the study period 1524 cases and their controls were accounted. Change in trend was observed in patients diagnosed at younger age of 57.48 ± 0.56 years in 2010 with adenocarcinoma unlike 62.89 ± 1.21 years in 2006. Females show increase in incidence of lung cancer in 2010, p value < 0.001 . The “active” smokers and years of smoking were significantly high among cases. The incidence of squamous cell carcinoma declined from 47.4% in 2006 to 15% in 2010 whereas adenocarcinoma increased, p value 0.001. Significant change in trend involving younger age at presentation specially for female who also show increased incidence of lung cancer has been observed. This hypothesis needs confirmation through further studies.