BACKGROUND: Food-related quality of life (FRQoL) measures the impact of diet, eating behaviours and food-related anxiety on quality of life. Patients often view food and eating as central to symptom management. This is the first study to examine FRQoL in patients with inflammatory bowel disease, celiac sprue, achalasia and eosinophilic oesophagitis. METHODS: A total of 289 adults aged ≥18 years completed self-report measures evaluating the use of dietary treatment, FRQoL and other psychosocial outcomes. Principal component factor analysis evaluated potential subscales within the Food-Related Quality of Life Scale (FRQoL-29), to date validated only with a total score. Univariate analyses investigated differences in FRQoL based on diagnosis, whereas correlations and hierarchical regression identified relationships between FRQoL and psychosocial outcomes. RESULTS: Factor analysis revealed four subscales within the FRQoL-29, with hypervigilance around eating being the primary driver in total score. Patients reported substantial impacts of FRQoL, with those not using diet therapy scoring significantly higher for FRQoL than those on a diet with and without the support of a registered dietitian (RD). Both social (r = 0.41, p < 0.001) and physical (r = 0.31, p < 0.001) domains of health-related quality of life were higher in patients with greater FRQoL. CONCLUSION: FRQoL is significantly degraded in patients with organic gastrointestinal illness diseases, and hypervigilance around food appears to contribute most to this. Use of dietary treatment and meeting with an RD were associated with lower FRQoL, though it is unclear if patients sought RD assistance before FRQoL declined. Future studies on the relationship between dietary treatment, RD support and FRQoL are warranted.