Objective To explore the nature, meaning and perceived origin of women's mental images of their breast cancer. Methods Fifteen women, who had completed treatment for primary breast cancer, participated in this qualitative in-depth interview study. Data were analysed using a constant comparative technique within the “Framework” method. Results Almost all women had a mental image of their cancer. Images reflected their beliefs about their illness (its appearance, character and dangerousness) and appeared to be related to a number of fears and concerns. The origin of images was uncertain but appeared to be influenced by scan images, verbal metaphors presented by health professionals, and previous beliefs held about cancer. Some women used metaphors presented to infer properties of the cancer that may have been unintended by the health professional. Conclusion Women may have mental images of their breast cancer that are associated with hope, reassurance, anxiety, despair, or views about the future. Further longitudinal research is required to establish the origin and importance of these images. Practice implications Health professionals may find that exploring women's mental images of their cancer is a helpful way of identifying potential misunderstandings about their illness