Introduction: Cement osseous dysplasia is the most common lesion of the family fibrous dysplasia which normal bone is replaced with fibrous tissue and several mineralized material. These lesions may be seen in association with various lesions. Companionship of this lesion with odontoma has been reported rarely.

Case report: A 44-year-old female in one year ago has admitted to Shahid Sadoughi Faculty of Dentistry Yazd for treatment of mandibular left third molar. In panoramic radiography in the mandibular left first molar region, a mixed lesion of radiolucent-radiopaque with a corticated borderwas seen. Small swelling was observed in this area. Microscopically, the diagnosis of osseous dysplasia with odontoma for the lesion was confirmed.

Conclusion: The reason of companionship of cement osseous lesions whit other lesions is not completely clear and it requires further evaluation.