BACKGROUND: The Inflammatory Bowel Disease Questionnaire (IBDQ) was developed by Guyatt et al. (1989) and it is the most widely used health-related quality of life instrument for patients with Crohn's disease (CD) and ulcerative colitis (UC). The aim of this study was to assess the psychometric properties of a Spanish version of the original IBDQ by examining the instrument's underlying factor structure, the internal and external validity, and the internal consistency reliability MATERIAL AND METHOD: One hundred and forty seven patients (76 CD, 71 UC) completed the Spanish version of the IBDQ, the Hospital Anxiety and Depression Scale (HADS) and the Temperament and Character Inventory (TCI). Clinical activity was assessed by the CDAI and the Truelove-Witts index. RESULTS: The confirmatory factor analysis of the IBDQ failed to reproduce the original four-factor structure proposed by Guyatt et al. We found that the Spanish version of the IBDQ consists also of four underlying factors, but the content of each factor and the items included were slightly different. Psychometric testing of the IBDQ revealed that the questionnaire has an acceptable internal and external validity, and a high internal reliability. CONCLUSION: Although confirmatory factor analyses failed to reproduce the original psychometric structure of IBDQ, it seems that the Spanish version of this instrument proved to be valid and reliable for assessing health related quality of life in inflammatory bowel disease patients.