Background: Laryngeal mask airway (LMA) has proven safe and effective for airway management in children during general anesthesia; mostly the second generation LMAs, none of which resulted clearly better despite previous studies. Aim: Proseal-LMA (PLMA) and Supreme-LMA (SLMA) are compared for structural characteristics and oropharyngeal leak pressure as primary aims, and mechanical ventilation, insertion, intra- and postoperative complications as secondary aims. Trial design: prospective randomised parallel clinical trial. Methods: instrumental evaluation: measurements of length, cross section, loading test on free air were performed to assess the resistance during ventilation. Then, 39 children received PLMA and 39 received SLMA for airway management during elective surgery: intraoperative and postoperative data were analyzed. Results: transversal section area was 35,71 mm(2) in PLMA and 59,61 in SLMA, whilst length was 133,67 and 123,07 mm; the loading test on free air confirmed lower resistance of SLMA. Oropharyngeal leak pressure resulted significant lower in SLMA. No significant difference in other clinical parameters and complications. Conclusions: instrumental measurements highlight that SLMA offers the advantage of less resistance to the airflow, allowing to keep lower oropharyngeal leak pressure during mechanical ventilation. Despite the differences reported, we observed only a few minor complications in both groups. (C) 2019 Elsevier Ltd. All rights reserved.