One of the criteria for functional constipation (FC) in Rome IV criteria is the presence of hard or painful bowel movements. In adults and children, the Rome IV criteria recommend the use of the Bristol Stool Scale (BSS). This scale is thought not to be appropriate for evaluation of stool consistency in young children. The Brussels Infant and Toddler Stool Scale (BITSS) was developed as a scale for children wearing diapers. There are no prior studies comparing BITSS with BSS in a clinical setting. Our main aim was that BITSS behaves differently than the BSS as it reflects better stool characterization by parents.Surveys were provided to parents of participants in two cities from Colombia which included the Rome IV-validated questionnaire and stool consistency assessment using pictures for BSS and BITSS.A total of 666 responses were obtained for non-toilet-trained children, mean age was 16.6 months. Detection for normal stools was higher using BSS (58.6%) when compared to BITSS (13.6%), and conversely was more likely to be abnormal through BITSS (86.4%) than BSS (41.4%) (p < 0.0001). BITSS (57.4%) was better than BSS (25.3%) identifying hard stools in FC (p = 0.000). For hard stools per parental classification, BITSS' definition was better than BSS (75.8% vs 44%, respectively, p = 0.000).The BITSS and BSS behave differently. The BITSS seems to be more sensitive to detect hard stools and FC than BSS. More studies are needed to better define whether BITSS is appropriate to replace BSS in non-toilet-trained infants and toddlers.