Cancers of the oral cavity and pharynx are the most common head and neck cancers in the United States, and squamous cell carcinoma is the most frequent histologic type. The clinical behavior and outcome of tumors in the oral cavity is distinct from those of the oropharynx. As a general rule, surgical resection is the primary treatment for oral cavity squamous cell carcinoma, whereas oropharyngeal squamous cell carcinomas are treated with radiation with or without chemotherapy. A clear understanding of the anatomy and knowledge of clinical behavior and spread patterns of oral cavity and oropharyngeal squamous cell carcinoma are essential for radiologists to make a meaningful contribution to the treatment of these patients.