Background and study aims Currently available polyethylene glycol (PEG)-based preparations continue to represent a challenge in children. The aim of this study was to compare the efficacy and safety of a new low-volume PEG preparation with a conventional PEG-electrolyte solution (PEG-ES) in children and adolescents. Patients and methods This was a multicenter, randomized, observer-blind, parallel-group, phase 3 clinical trial, where patients were randomized between PMF104 (Clensia) and a conventional PEG-ES (Klean-Prep), and stratified by age stratum (2 to <6; 6 to < 12;12 to <18 years). The primary endpoint was to test the non-inferiority of PMF104 versus PEG-ES, in terms of colon cleansing. Safety, tolerability, acceptability, palatability, and compliance were also assessed. Efficacy endpoints were analyzed in the per protocol set (PPS) and full analysis set (FAS) and safety and tolerability endpoints in the safety set (SAF). Results Of the 356 patients enrolled, 258 were included in the PPS, 346 in the FAS, and 351 in the SAF. Non-inferiority of PMF104 was confirmed for children aged > 6 years and for all age groups in PPS and FAS, respectively. Optimal compliance was reported more frequently in the PMF104 than in the PEG-ES group, in both PPS (86.1% vs. 68.4%) and FAS (82.9% vs. 65.3%). Both preparations were equally safe and tolerable. Palatability and acceptability were considered better in the PMF104 group than in the PEG-ES group (27.1% vs. 15.3% and 15.3% vs. 3.5%, respectively). Conclusions In children aged 6 to 17 years, the new low-volume product PMF104 is non-inferior to the reference PEG-ES in terms of bowel cleansing, safety, and tolerability, with slightly better results in compliance, palatability, and acceptability.