The cementoblastoma is a rare odontogenic tumor occurring in the mandibular molar and premolar of the patients in the second and third decades of life. Despite its typical benign behavior, this tumor may promote local destruction by perforating the cortical bone and displacing the mandibular canal. This case report shows a 31-year-old man with an aggressive cementoblastoma attached to the apex of the mandibular first molar. Cone-beam computed tomography revealed a hyperdense mass connected to the root of mandibular molar surrounded by a hypodense area. Multiplanar reconstructions showed rupture of buccal bone plate and tumor invasion of the mandibular canal roof. The surgical planning included enucleation of tumor with the first and second molars extractions and the diagnosis of cementoblastoma was confirmed by histopathology. This case report emphasizes the contribution of cone-beam computed tomography on diagnosis and appropriate surgical planning of the cementoblastoma. Key words: Cone-Beam computed tomography, odontogenic tumors, diagnosis.