Background: Poor adherence frequently impaired the efficacy of therapy to maintain remission from inflammatory bowel diseases (IBD). There is a lack of practical and effective interventions to improve adherence. This study aimed to identify modifiable risk factors, which may yield targets for new interventions. Methods: Participants with IBD were recruited from hospital outpatient clinics and office-based gastroenterologists. Demographic and disease-related data were recorded by means of self-administered questionnaires. Modifiable risk factors were assessed with the validated Belief about Medicine Questionnaire, Hospital Anxiety and Depression Score, and short inflammatory bowel disease questionnaire. Adherence was assessed separately for 5-aminosalicylates, thiopurines, and biological agents using the validated Medicine Adherence Report Scale (good adherence defined as >16). Results: Nonadherence occurred in 102 of 356 participants (28.7%). Adherence increased significantly with more aggressive therapies (median Medicine Adherence Report Scale: 5-aminosalicylates 18, thiopurines 19, biological 20; P <0.0001). Nonadherence was not associated with anxiety and depression or disease-related patient knowledge. Adherent patients had significantly higher belief of necessity for medication (P <0.0001) and a trend toward lower concerns about medication (P = 0.08). Membership of an IBD patient organization was associated with better adherence (P <0.0001). Concerns about medication rose significantly with more aggressive therapies (P = 0.009), but belief of necessity was similar for all medications. Conclusions: Nonadherence occurs most frequently with 5-aminosalicylates. Belief of necessity may prove the key target for future interventions, although general IBD education is unlikely to yield an adherence benefit. Patient organization membership should be encouraged. Copyright © 2013 Crohn's & Colitis Foundation of America, Inc.