OBJECTIVES: To explore the existence and importance of mental images of cancer among people with head and neck cancers with a focus on the perceived origins and meaning of mental images, their development over time, and their relationship to illness beliefs. METHODS: A longitudinal qualitative study consisting of 44 in-depth semi-structured interviews with 25 consecutive, newly-diagnosed head and neck cancer patients. Participants were invited to draw their images during the interviews. Follow-up interviews occurred after treatment completion. Analysis drew upon the principles of Interpretative Phenomenological Analysis (IPA). RESULTS: Many participants had mental images of their cancer which appeared to both embody and influence their beliefs about their illness, and affect their emotional response. For those who held them, mental images appeared to constitute an important part of their cognitive representation (understanding) of their illness. For some, their images also had a powerful emotional impact, being either reassuring or frightening. Images often appeared to originate from early clinical encounters, and remained fairly stable throughout treatment. Images could be conceptualised as 'concrete' (the perceived reality) and/or 'similic' (figurative). Patients' images reflected the perceived meaning, properties or 'intent' of the cancer-that is beliefs concerning the disease's identity, consequences and prognosis (likelihood of cure or control). CONCLUSIONS: People with head and neck cancer may develop a mental image of their disease, often generated early within clinical encounters, which can both reflect and influence their understanding of the cancer. Such images tend to be stable over time. We theorise that careful use of images in early consultations could avoid or minimise some distress, including fears of outcome or recurrence. Concrete or similic images and language could be employed later to change perceptions and reduce distress.