 The diet and bowel function questionnaire was developed and validated to measure the impact of diet on bowel function in children. It consists of 13 questions assessing the significance of certain foods for bowel function, emotional responses related to eating, and the effects of 90 specific food items on bowel function. The questionnaire was designed to be answered by children, and the content validity was tested during two semi-structured interviews with different participants and a pilot test with a third cohort. The final version of the questionnaire was presented at the end of the validation process, detailing the reasons for the selected question and answer options and their wordings. This article was authored by Lovis Atelborn, Christine Cumblian, Christina Grinelli, and others.