We describe a rare case of mandibular highflow arteriovenous malformation (AVM) mimicking an odontogenic cyst in a young man. The diagnosis of mandibular AVM was made by CT angiography and confirmed by digital subtraction angiography. CT scan showed the extent of mandibular bone alteration and a double enlarged mandibular canal on the same side. An AVM containing a large aneurysm was demonstrated by CT angiography.The mandibular AVM was successfully treated by endovascular therapy with Guglielmi detachable coils. On panoramic radiogram, mandibular AVMs can appear as cystic lesions without pathognomonic features. Several benign and malignant tumours of this anatomical region must be considered in the differential diagnosis.We emphasize the radiological sign of double enlarged mandibular canal and the diagnostic role of CT, particularly CT angiography, to discriminate a mandibular AVM from neoplastic entities of this region, sparing the risks of a needle biopsy.