This article analyses the experience of former cancer patients who, many years after the treatment of their illness, suffer from ‘extreme persistent fatigue’. The aim is to demonstrate how this symptom can be experienced as problematic and to detail coping strategies that individuals use in order to live with it. This qualitative exploratory study took place in the Netherlands and was based on semi-structured interviews with 12 former cancer patients suffering from extreme fatigue 7–10 years after their illness was treated. The aim of the informants is to achieve a medical diagnosis of cancer-related fatigue, which increases their chances of receiving care and understanding, and thus gives a social and medical legitimacy to their suffering. The search for legitimacy appeared to be especially evident in the demands for disability allowances. Counselling and care in cancer patients should be more focused on the prevention of persistent fatigue during and after cancer diagnosis and treatments.