In the past the benign cementoblastoma was recognized in the World Health Organization's classification of odontogenic tumours as one of the cementoma neoplasias. Recently the benign cementoblastoma is included into Mesenchyme and/or odontogenic ectomesenchyme, with or without odontogenic epithelium odontogenic tumours. Benign cementoblastoma has characteristic radiologic and microscopic features and it appears to be fused to the tooth roots. Symptoms may be totally absent, and when they do occur, pain and swelling are frequent findings. The final diagnosis is usually made histopathologically, but the clinical diagnosis is comparatively easy if it is examined radiographically. The tumour has unlimited growth potential. Most frequently tends to be associated with an erupted permanent tooth, most often the first molar: rarely has an association with an impacted or partial impacted tooth been reported. This case represents a case of benign cementoblastoma associated with a partially impacted mandibular third molar.