Background: Reactive oxygen species [ROS] if produced in large amounts, have destructive effects because of high reactivity. During oxidative stress there is an imbalance between the formation of free radicals and antioxidant defence mechanisms through damaging cellular macromolecules. Smoking is one of the major risk factor that affects the prevalence, degree and severity of periodontal disease. AIM: . The purpose of the present study is to evaluate and compare the levels of ROM in GCF, saliva and plasma in smokers and non-smokers with periodontitis MATERIALS & METHODS: 30 Participants (males) were selected and were divided into two groups Group I - Smokers with Chronic Periodontitis and Group II - Non-Smokers with Chronic Periodontitis with 15 each . GCF, Saliva and Plasma were collected from both the groups and were tested in the laboratory through the principle of Fenton’s reaction. RESULTS: One way ANOVA analysis and paired t test were used for analysis .On comparison of ROM levels in smokers and non-smokers, level of ROM was increased in smokers and it was highly significant with p value ≤ 0.05. CONCLUSION: Free radical production mediated by cigarette smoke is highly toxic and impaired oxidant-antioxidant balance is a risk factor for periodontal disease, as the results from the present study suggested increased levels of ROM in smokers