We present two clinical cases of radiolucent mandibular lesions in young women that simulated chronic periapical infectious pathology. The detection of both cases was fortuitous since they were totally asymptomatic. Diagnosis was reached in one case (upon periapical surgery and anatomo-pathologic study) after endodontic treatment and after verifying non-resolution of affected periapical area. The other case was an extensive lesion, which involved the periapices of the four inferior incisors in which surgery was directly performed upon verifying pulp vitality of these teeth. After surgery endodontic treatment was performed on the teeth that had lost their vitality. In both cases the histopathologic tests revealed the presence of a cemento-ossifying fibroma, the initial clinical and radiographic diagnosis of which could easily be overlooked.