BACKGROUND: Feline Odontoclastic Resorptive Lesion (FORL) is one of the most common diseases in oral cavity of adult domestic cats. OBJECTIVES: Evaluation of different types of FORL by radiography and computed tomography in order to accurately and early diagnose of disease. METHODS: In this retrospective study during 1 year, among 68 CT scans and 17 radiographs of the head of referral cats to veterinary hospital, University of Tehran, 18 cases of FORL (10 CT scans and 8 radiographs) having different degrees of teeth involvement in accordance with stages of FORL were described and diagnosed. For this purpose, radiographic images of teeth in lateral, oblique and dorsoventral views were prepared and also CT images of 2D in transverse, sagittal and dorsal views and 3D were constructed for evaluation of dental and bones reactions. RESULTS: In radiography and computed tomography, FORLs lesions are classified into five stages. In Stage 1 there is mild cementum and enamel loss but this stage is usually not noted on dental radiographs but may be felt on clinical exploration. In Stage 2 there is moderate cementum and enamel loss with dentinal loss that does not involve the pulp. In Stage 3 there is severe loss involving the pulp cavity with remaining  tooth integrity. In Stage 4 there are extensive dental hard tissue losses and most of the tooth has lost its integrity. In Stage 5 there are remnants of dental hard tissues as irregular opacities. Furthermore, in this study it was proved that FORL occurs in male more than female cats and mandibular premolar teeth are the most affected ones. CONCLUSIONS: Considering that FORL has different stages and consequently has different severity, accurate diagnosis of this disease by radiography and computed tomography can help prevent progression of disease and results in fast and successful treatment.