Objectives: Psychosocial factors have been examined in functional bowel disorders (FBD), including irritable bowel syndrome (IBS) and chronic idiopathic constipation (CIC). Abnormal illness behaviour (AIB) has been investigated in IBS patients as evidence of underlying psychological distress and as influencing health-care-seeking behaviour. Health locus of control may also contribute to health-care-seeking behaviour, as possession of an external locus of control places responsibility for health status onto professionals. Thus, external locus of control may also be more prominent in FBD patients. This study examined whether FBD patients displayed more AIB and an external health locus of control compared with organic disease and non-patient controls. Design: A cross-sectional comparison group design was employed. Method: Fifty-three CIC patients were compared with matched control groups of 50 IBS patients, 51 Crohn's disease patients and 53 non-patient participants. Questionnaire measures included the Illness Behaviour Questionnaire, the Multi-dimensional Health Locus of Control, the GHQ, and the SCL-90R. Results: FBD patients did not differ from Crohn's disease patients on measures of AIB, but all three patient groups differed from non-patient participants. Crohn's disease patients possessed a higher external locus of control compared with FBD patients and non-patient controls. There was a general association between AIB and psychopathology. Conclusions: FBD patients did not report more AIB or a higher external locus of control regarding their health status, compared with organic disease controls, but did differ from non-patients. The presentation of AIB was related to increased psychopathology, suggesting that AIB may be related to psychological distress, irrespective of patient status.