BACKGROUND & AIMS: There are concerns about levels of radiation exposure among patients who undergo diagnostic imaging for inflammatory bowel disease (IBD), compared with other gastrointestinal (GI) disorders. We quantified imaging studies and estimated the cumulative effective dose (CED) of radiation received by patients with organic and functional GI disorders. We also identified factors and diagnoses associated with high CEDs. METHODS: We analyzed data from 2590 patients who were diagnosed with GI disorders at a tertiary gastroenterology center from January 1999-January 2009 on the basis of International Statistical Classification of Diseases and Health-related Problems, 10th revision and Rome III criteria. High annual CED and high total CED were defined as figures exceeding the 90th percentile for the population. RESULTS: Diagnostic imaging was performed on 57% of the patients (1429 of 2509). High annual CEDs (>9.6 millisieverts/annum) were independently associated with Crohn's disease (odds ratio [OR], 5.3; P < .0001), organic small bowel disease (OR, 2.6; P < .005), and functional disorders of childhood and adolescence (OR, 9.8; P < .005). High total CEDs (>30.8 millisieverts) were independently associated with Crohn's disease (OR, 81.9; P < .0001), ulcerative colitis (OR, 19.0; P < .0001), indeterminate colitis (OR, 7.5; P < .0005), and the following non-IBD diagnoses: organic small bowel disorders (OR, 12.5; P < .0001), organic hepatic disorders (OR, 3.6; P < .01), and functional disorders of childhood and adolescence (OR, 13.8; P = .02). CONCLUSIONS: Higher levels of annual and total diagnostic radiation exposure are associated with IBD and with other organic and functional GI disorders. Evidence-based guidelines for image analysis of patients with organic and functional gastrointestinal disorders, especially those that reduce radiation exposure, are needed.