BACKGROUND: The use of complementary and alternative medicine in inflammatory bowel disease patients is progressively increased. AIM: To evaluate the use of complementary and alternative medicine in inflammatory bowel disease patients and to know potential risk factors for their use. The subjective response of these therapies and the impact on treatment adherence were also evaluated. METHODS: Prospective, descriptive and transversal study. Inflammatory bowel disease patients were classified according to demographic and clinical characteristics. A questionnaire about the use of complementary and alternative medicine was collected. RESULTS: 705 patients were included. 126 patients (23%) had used complementary and alternative medicine. The most commonly used was herbal remedies (n=61), homoeopathy (n=36), acupuncture (n=31), kefir (n=31) and aloe vera (n=25). Factors associated with its use were extraintestinal manifestations (OR 1.69, CI 95% 1.11-2.57) and long-term evolution of the disease (OR 2.08, CI 95% 1.44-2.99). Most patients (74%) had the subjective feeling that use of complementary and alternative medicine had not improved their condition, 11 had adverse events related to its use and 11% of patients discontinued their conventional drugs. CONCLUSIONS: Use of complementary and alternative medicine in inflammatory bowel disease patients is frequent, especially in those with extraintestinal manifestations and long-term evolution. The use of these therapies was not perceived as a benefit for patients.