Lingual mandibular bone defects, also known as Stafne bone cavity (SC), are unilateral asymptomatic radiolucencies, generally seen in the mandibular angle, below the inferior alveolar canal. Although panoramic radiographies normally offer enough information to make a correct diagnosis, additional studies are often required, especially in atypical cases. The present report describes an atypical presentation of a Stafne's bone cavity in a 78 years-old male patient. In this particular case, an asymptomatic and radiolucid lesion was observed during a routine dental examination. The computed tomography (CT) showed an involvement of both lingual and buccal mandibular plates producing a tunnel-like lesion. No history of mandibular trauma or surgery was refered. An additional magnetic resonance imaging (MRI) was made to discard submandibular gland pathology and to confirm the diagnosis. Since SC is asymptomatic and nonprogressive, a conservative approach based in clinical and radiological follow-ups was considered to be the most suitable treatment option.