The current study aims to investigate the differences in illness representations in participants with chronic fatigue syndrome (CFS) and lupus. The study also examines the relationships between illness representations and coping strategies in both CFS and lupus. Eighty-two CFS participants and fifty lupus participants completed the Illness Perception Questionnaire-Revised and the Brief COPE Inventory. The study employed an independent samples design. The independent variable is whether the participants have lupus or CFS. The dependent variables are the twelve dimensions of illness representations and the fourteen positive and negative coping strategies. The results show a significant difference in the illness perception subscales of identity, timeline, time-cycle, personal control, cure-control, illness coherence, and causal attributions. The results also show significant relationships between illness representations and coping strategies in both the CFS and lupus group. The CFS group had more negative beliefs about their illness in relation to illness identity, personal control, treatment control, and illness coherence than the lupus group. This supports the literature that CFS sufferers have more negative illness perceptions than do patients with a clearly recognised and potentially disabling chronic illness.