Radiation therapy is frequently used method in treatment of the head and neck 
malignancies. Osteosarcoma is a rare complication of radiation therapy and 
usually occurs after a long latent period. We report the case of 75-year-old 
female with osteosarcoma of the mastoid process. Twelve years before 
presentation she received radiation therapy after total parotidectomy and 
radical neck dissection in treatment of mucoepidermoid carcinoma of the parotid 
gland. Diagnostic procedures included contrast-enhanced CT and MRI of the head 
and neck and HRCT of the temporal bone. The final diagnosis of the low grade 
osteosarcoma was confirmed by biopsy. Diagnostic criteria were fulfilled and the 
lesion was classified as a radiation induced osteosarcoma.