Dermoid cysts develop from sequestration of epithelium along lines of embryonic fusion.The most common locations are the lateral third of the eyebrows, nose, and scalp. These cysts are located in the subcutis;they are often adherent to periosteum, and may invade or erode underlying bane. A 34-year-old female presented with a solitary, skin colored, dome-shaped, child fistsized, subcutaneous mass on her right occiput. At operation, keratinous material was discharged and tufts of hair projected from opening of the cyst wall.The base of the cyst was firmly adherent to periosteum and diffuse depression with focal deep erosions of the outer table of skull was found.