To determine the proportion of complementary and alternative medicine (CAM) use in patients with inflammatory bowel disease (IBD) and to identify demographic and clinical factors that are associated with CAM use. In this cross-sectional study design, patients with confirmed diagnosis of ulcerative colitis (UC) or Crohn's disease (CD), and ≥18 years old, attending outpatient clinics at 14 hospitals in Norway were eligible to complete questionnaires including demographics, clinical variables, and the International CAM Questionnaire (I-CAM-Q). Of 460 patients included in the study, 430 had evaluable questionnaires (response rate 93%). Forty-nine percent (95% CI: 44-54) had used some type of CAM within the past 12 months. CAM services were utilized by 27% (95% CI: 23-31) of the patients, 21% (95% CI: 16-23) reported use of CAM products, and 28% (95% CI: 23-31) used CAM self-help practices. The most common pattern of CAM use was to combine CAM services and CAM products. Significantly, more UC patients (56%) than CD patients (44%) reported CAM use, p = 0.03. In UC, only the presence of at least one comorbid condition was directly related to CAM use. In CD, being a woman, being aged 31-50 years, having a higher education level, and experiencing adverse drug reactions from IBD medication were factors independently associated with the use of CAM. Use of CAM was common among IBD patients attending outpatient clinics. Both demographic and clinical factors were associated to CAM use, but the factors differed in their significance for UC and CD.