We present the second case of Klippel-Feil syndrome in association with a posterior fossa dermoid cyst extending through the occipital bone and presenting as a suboccipital subcutaneous mass. We describe its radiographic, CT, and MRI appearances as well as on MRI diffusion-weighted images. Posterior cranial fossa dermoid cysts and sinuses should be added to the list of congenital abnormalities which must be sought in patients with Klippel-Feil syndrome. Diffusion-weighted images of brain may differentiate these masses from cerebral spinal fluid collections.