We report here on a rare case of lipoma in the deep lobe of the parotid gland. MRI revealed that the tumour was situated mainly in the deep lobe and it extended posteriorly and medially into the space between the sternocleidomastoid muscle and the posterior belly of the digastric muscle, with slight extension into the parapharyngeal space. This tumour produced strong signals on T1- and T2-weighted MR images and weak signals on fat suppression images. In addition, MRI clearly showed the margin of the tumour, which enabled us to readily distinguish the tumour from the surrounding adipose tissue. The images suggested a diagnosis of deep lobe parotid lipoma with posteromedial extension to the sternocleidomastoid muscle, which proved true at surgery. We thus believe that MRI is highly useful, perhaps even necessary, in diagnosing tumours of the head and neck.