Desmoplastic fibroma (DF) is a rare non-metastasizing benign neoplasm of the bone characterized by aggressive local infiltration, also known as desmoid tumour. Desmoplastic fibroma of the mandible may recur locally when incompletely excised. In particular it can occur adjacent to and display contiguous extension along the mandibular nerve. This case report describes the imaging findings of a histopathologically proven desmoplastic fibroma involving the right mandibular region in a three-year-old Italian girl. We also discuss the usefulness of different imaging modalities (CT and MRI) in DF diagnosis and treatment.