Background and objective: Head and neck squamous cell carcinoma is one of the most common cancers. Important risk factors is use of tobacco and alcohol. Late diagnosis and lack of treatment of oral pre-cancerous lesions lead to develop cancer. Therefore, in this study we assessed the frequency of oral lesions in tobacco products and alcohol and other addictive substances users in patients referred to Mashhad dental school. Methods: This cross-sectional study was performed on 401 patients (200 consumers of tobacco products, alcohol and other addictive substances and 201 patients, who did not have any consumption history) from the patients referred to Mashhad Dental School. Data were collected using a questionnaire and clinical examination then analyzed by Statistical tests: Chi-square, Chi-square and logistic regression. Findings: The mean age in the case and control groups was 41.28 ± 12.71, 40.16 ± 14.81, and 87.5% of subjects in the case group and 55.7% in the control group were males. The most common substance was cigarette (57%). A significant correlation was found between smoking and pigmentation (P <0.001), fissured tongue (P <0.001), hairy tongue (P = 0.004), and plaque-like candidiasis (P = 0.014). Relationship between hookah with lichen planus, and pan with tobacco-pouch were significant (p = 0.003, p <0.001, respectively). Conclusion: The most frequent substance was cigarette in the men and hookah in the women. The most common oral change was pigmentation. The majority of pan users had pre-cancerous lesions in the mouth.
