Abstract: Background: Lung cancer is a type of cancer that arises in the lungs. Adenocarcinoma and squamous cell carcinoma are the two major subtypes of non-small cell lung carcinoma. Material and Methods: This is a retrospective study conducted in the Department of Pathology, over a period of 1 year at a tertiary care hospital and teaching centre. A total of 125 cases comprising of 70 adenocarcinomas and 55 squamous cell carcinomas of lung were included in the study. Result: All 27 cases of well differentiated Adenocarcinoma were negative for P40 and 1 case showed positive P63 expression. Out of 43 cases of moderately differentiated Adenocarcinoma, 1 case was positive for P40 and 4 cases were positive for p63. Out of 19 cases of well differentiated Squamous cell carcinomas 18(94.7%) cases were positive for P40 and 18 (94.71%) cases were P63 positive. All 36 (100%) cases of moderately differentiated Squamous cell carcinoma showed positive P40 and P63 expression. Conclusion: Strong and diffuse P40 expression was noted in majority of lung squamous cell carcinomas and absence of P40 in most of the lung adenocarcinomas. Thus, p40 is an excellent marker for distinguishing lung squamous cell carcinoma from adenocarcinoma, and that its expression is equivalent to that of p63 in lung squamous cell carcinoma. Since P63 shows variable expression in lung adenocarcinomas; in moderately differentiated cases, a two-panel approach of p63 and p40 help to distinguish adenocarcinoma from squamous cell carcinomas.