Introduction: Smoking is most common among the men aged 15 and above accounting for 51% of the population. The rate at which the adolescent boys use tobacco is 18% globally [GHO, WHO]. In India, an estimated 82.3% males with COPD are smokers. Oxidative effect via free radical generation in smokers has been widely investigated, as it causes the lipid peroxidation, damage to tissues primarily Lung apart from the cardiac diseases. Objective(s) of Study: To estimate the serum levels of Adenosine Deaminase (ADA), Malondialdehyde (MDA), advanced oxidation protein products (AOPP) in smokers, & correlate with Spirometric changes in them. Material and Method: This is a crossectional observational analytical study conducted for a duration of six months at a Medical College Hospital in Mangalore city. A total number of eighty healthy individuals who visited medicine opd were included in this study. Out of these subjects, forty were smokers and other forty nonsmokers. Results: The results were analyzed in the SPSS-23version. A significnat high level of serum MDA, AOPP and low levels of ADA was observed in smokers when compred to non-smokers. Spirometric analysis showed statistical significant decrease in FEV1 (58.5?12%) in smokers. A significant inverse relation of the MDA, AOPP with Spirometric changes & positive relation of ADA levels with spirometry was also observed. Discussion & Conclusion: From this study, it is clear that the smokers are at a high risk of pulmonary diseases. The utility of these parameters as markers for the oxidative damage and variation in lung function test may be a useful tool in educating smokers regarding the ill effects with possible health derangement & urge them to quit smoking.