PURPOSE: The aim of this study was to compare the results of the retroperitoneoscopic assisted pyeloplasty (RASP) using EZ access (silicone rubber cap) with open dismembered pyeloplasty (ODP) in children. METHODS: A retrospective review was performed of patients treated for ureteropelvic junction (UPJ) obstruction with either RASP or ODP from 2010 to 2015. For patients with RASP, two 5-mm trocars were placed in the EZ access. The UPJ was dissected retroperitoneoscopically and dismembered pyeloplasty was performed extracorporeally. Patient demographics and operative outcomes were compared between the groups. RESULTS: A total of 50 children were included, with 25 RASP and 25 ODP. Mean patient age was 49months in the RASP group and 53months in the ODP group. Perioperative outcomes, including operative time (185 vs 188min) and postoperative hospital stay (2.0 vs 2.2days), were similar between the two groups. Mean skin scar length (17 vs 34mm) was significantly smaller in the RASP group. The postoperative success rate (96% vs 100%) was not significantly different between the groups. CONCLUSIONS: The RASP represents a safe and effective single-site procedure in children. This procedure significantly reduces the skin scar length and has equivalent surgical outcomes to ODP. THE TYPE OF STUDY: Retrospective comparative study. LEVELS OF EVIDENCE: III.