Primary intraosseous squamous cell carcinomas (PIOSCCs) are rare malignant tumours which arise from odontogenic epithelial remnants. Herein we report five new PIOSCC cases, affecting three female and two male patients with a mean age of 64.4 years. One case involved the maxilla and four cases occurred in the mandible. Typical radiographic findings were ill-defined radiolucencies. Histopathologically, four cases were diagnosed as well-differentiated PIOSCCs arising de novo or from odontogenic cysts. The remaining case was a moderately differentiated de novo PIOSCC. In four cases, treatment consisted of surgical removal with perioperative radiotherapy or chemotherapy. To date, there have been no recurrences or distant metastases in three cases. The lesion was not locally controlled in one case and curative treatments were rejected in another case. PIOSCCs are thought to be important among radiolucent jaw lesions, and early diagnoses and surgical excision with sufficient margins of safety may allow for good prognoses.