The oral cavity is a complex anatomical region consisting of different anatomical sites and subsites. Cancer undoubtedly represents the most frequent and relevant disease of this region. Clinical examination is often the first approach to oral cavity tumours. Cross-sectional computed tomography (CT) and magnetic resonance imaging (MRI) play a key role in staging locoregional disease by demonstrating submucosal spread and involvement of deep layers; evaluation of specific pathways of spread to peculiar anatomical subsites is also fundamental information that can be obtained with these techniques. The purpose of this paper is to illustrate CT and MRI findings of anatomical subsites involved by tumours of the oral cavity.