BackgroundAlthough dietary adjustments are recommended frequently for bowel symptoms, evidence of diet’s impact on bowel function is lacking. The aim was to develop a patient-reported outcome instrument, for children with and without Hirschsprung’s disease (HD), to explore experiences of dietary effects on bowel function.MethodsChildren with and without HD and their parents participated. Questionnaire items regarding the impact of diet on bowel function originated from focus group discussions. Specific food items, reported in the literature or in focus groups to cause bowel functional effects, were listed requesting each item’s effect size and effect type. Content validity was tested within two separate semistructured interviews. A pilot test was performed. Assessing comprehension, relevance and wording clarity structurally, revisions were made accordingly. Children’s bowel function was assessed through the validated Rintala Bowel Function Score.ResultsA total of 13 children with and without HD, median age 7 (range 2–15) years, and 18 parents participated in the validation. Each question’s relevance had been ranked highly early in the validation process but most questions needed refining for improving clarity and comprehension. Wordings regarding bowel symptoms and emotions connected to food in particular were perceived to be sensitive and complex. Specifically wording regarding some bowel symptoms (gases, pain) and parental stress emotions (guilt, ambivalence) were, consistent with participants’ opinions, subjected to multiple step revisions. Following the validation process, which included two semistructure interviews with different participants and then a pilot test with a third cohort, a full track overview of changes and rewording made in all steps of the validation process was presented. The final questionnaire then comprised 13 questions assessing foods’ significance for bowel function, emotions, social impact and 90 specific food items’ possible effects and effect sizes on bowel function.ConclusionsThe Diet and Bowel Function questionnaire, enabling answering by children, was developed and the content validated qualitatively. This report presents insights into the whole validation process, declaring reasons for the selected question- and answering options, and their wordings. The Diet and Bowel Function questionnaire can be used as a survey questionnaire to enhance understanding of dietary effects on bowel function in children, and its results can be supportive in improving dietary-treatment programs.Supplementary InformationThe online version contains supplementary material available at 10.1186/s40795-023-00737-6.