Aim: The aim of this project is to study the cytomorphometric features of effect of tobacco chewing on buccal mucosa and to identify its role in early diagnosis of oral cancers in tobacco chewers. Methods: Total 100 patients, including 20 control and 80 patients with history of tobacco chewing were included in the study. They were divided into five groups as Group N: Control; Group A: subjects with tobacco chewing habit but without any lesion; Group B: subjects with tobacco-lime lesion; Group C: leukoplakia; Group D: oral squamous cell carcinoma. Oral cytology smears were obtained using cytobrush technique. Smears were stained with Papanicolaou stain. The cellular and nuclear diameter were measured using ocular micrometer. Statistical analysis was carried out using Analysis of Variance (one way ANOVA) Results: The cellular diameter was progressively reduced from normal, through history of tobacco chewing but without lesion, tobacco-lime lesion and leukoplakia to oral squamous cell carcinoma. We found decrease in the mean cellular diameter, increase in the nuclear diameter and ratio of nuclear diameter to cellular diameter. On statistical analysis P value of cellular diameter was 0.003 and for nuclear diameter was 0.000, which was highly significant. Conclusion: Cytomorphometry is a simple, noninvasive diagnostic technique to assess the influence of tobacco on buccal mucosa. This helps in early detection of premalignant changes and improves the prognosis by early intervention.