Background and aims. A correct diagnosis is the most important step in the treatment of oral lesions and each oral lesion has specific clinical features that provide clinical diagnosis; however, some of these features are common among different lesions. In these situations, biopsy and histopathological examination are indicated. The aim of this study was to evaluate the relationship between clinical and histopathological diagnosis of patients referred to the Department of Oral Pathology, Tabriz Faculty of Dentistry, from 2009 to 2011. Materials and methods. In this retrospective study, individual data and clinical findings of 311 patients who had been referred to the Department of Oral Pathology during a three-year period were collected through questionnaires and compared with histopathological reports. Data were analyzed by using chi-squared and Fisher's tests. Results. In 80.7% of the cases the clinical diagnosis of the lesions was consistent with pathology reports. In 19.3% of the cases, the clinical diagnosis of the lesions was not confirmed histopathologically. The greatest consistency was observed for lichen planus (100%) and inflammatory fibrous hyperplasia (epulis fissuratum) (94.3%). Conclusion. Although great consistency rates were observed in this study between clinical diagnoses and pathology reports, there was also a significant disagreement with the literature, indicating that comprehensive clinical examination, high consistency with oral lesion features and effective cooperation between surgeons and pathologists are necessary.