Gastric cancer is one of the most common cancers in the world and in the north and northwest of Iran. Given a high prevalence of polycyclic aromatic hydrocarbons (PAHs) in the environment as one of the influential factors in cancer, the present study was conducted to evaluate the relationship between tissue levels of polycyclic aromatic hydrocarbon (PAHs) and history of food exposure to environmental contaminants. Immunohistochemistry was performed in patients with gastric cancer. The study population included 30 patients with gastric cancer. Thirty tissue samples were randomly selected among patients with gastric cancer and a questionnaire was used to assess the role of environmental factors and nutritional factors in the incidence of gastric cancer. Patients' tissue blocks were examined by BPDE-5D11 monoclonal antibody to determine the tissue expression of PAH using immunohistochemistry (IHC). Statistical analysis of data was performed using SPSS16 software. The results showed that the tissue level of PAH is associated with factors such as the place of birth of patients (rural or urban), gender of patients (male and female), type of PAH expression (diffuse, focal), and smoking (p <0.05). Also, investigation of PAH agonists in this study showed that smoking increases the risk of gastric cancer. Based on the results of the present study, it is recommended that contact with PAH sources such as smoked and grilled foods and cigarette smoke to be strictly avoided.