OBJECTIVES: Using patient-reported and observer-reported outcome measures to assess symptoms in children is challenging.  While the child is arguably the most ‘valid’ reporter, parents may provide more reliable responses.  Our aim was to assess the agreement in child and parent ratings of CC/IBS-C symptoms collected through an electronic daily diary (eDiary). METHODS: Separate child and parent eDiaries were developed to assess CC/IBS-C symptoms based on concept elicitation interviews with 64 children and 75 parents.  The eDiaries were completed by 36 children (aged 6-11) and 30 parents for 5-9 days prior to cognitive debriefing interviews.  eDiary data were compared for five symptoms: abdominal pain, bowel movement (BM) frequency, stool form/consistency, straining and rectal pain during defecation. RESULTS: There were moderate to high levels of agreement (children/parents selecting the same level of response on a given day) for all items, including 66.9% agreement for BM frequency; 70.2% for stool form and 72.5% for rectal pain. Children’s reports of their ‘tummy hurting’ were consistent with parents seeing  their child holding his/her tummy (68.5% agreement) and parents being told by the child that  his/her tummy hurt (76.4% agreement).  Children’s reports of straining were consistent with parents observing their child making a face (60.4% agreement) and hearing their child grunt (52.3% agreement) during defecation. Across all symptoms, agreement was higher for 6-8 year old children and their parents (mean 76.9% agreement) compared to 9-11 year old children and their parents (mean 58.4%). CONCLUSIONS: The results present evidence of moderate to strong agreement between children’s and parents’ reports of core CC/IBS-C symptoms.  Lower levels of agreement in ratings amongst 9-11 year old children and their parents may be due to parents being less aware of their child’s symptoms.