Food-related quality of life in patients with inflammatory bowel disease and irritable bowel syndrome, Abstract Background Food-related quality of life (FRQoL) evaluates the impact of diet, eating behaviors, and food-related anxiety on a person’s quality of life. This is the first study to evaluate FRQoL in inflammatory bowel disease (IBD) and irritable bowel syndrome (IBS), two illnesses where food and diet are of importance. Methods One hundred seventy-five participants (80 IBS, 95 IBD) participated in the study by completing measures evaluating FRQoL, psychological distress, and health-related quality of life. Primary analyses evaluated differences in FRQoL between IBD and IBS patients. Secondary analyses compared differences based on remission status, dietary use, and dietary consultation, as well as evaluated potential predictors of FRQoL. Results IBD patients in remission report the highest FRQoL (IBD-remission: 91.2 (26.5) vs. IBD-active: 67.7 (19.6) and IBS-active: 67.6 (18.3), p < .001). Using more dietary treatments is associated with decreased FRQoL for IBS (r = − 0.23, p < .05) and IBD patients (r = − 0.31, p < .01). IBS patients are more likely to use dietary treatments than IBD (IBS = 81% vs. IBD = 64%, p < .01), with self-directed diets being the most commonly used approach. Symptom severity is the strongest predictor of FRQoL in both groups (IBD: R2 = .27, p < .01; IBS: R2 = .23, p < .001). Conclusion FRQoL is a unique construct for IBD and IBS patients that can be influenced by several clinical and dietary factors, including number of diets and type of diet used, depending on the diagnosis. Thus, FRQoL should be considered when working with both IBD and IBS patients.