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BACKGROUND/OBJECTIVES Variations in vascular anatomy (VIVAs) of the retroperitoneal great vessels are uncommon but can potentially complicate surgical procedures and negatively affect treatment outcomes, yet their incidence and clinical impact are poorly studied. We sought to assess the incidence and clinical impact of VIVAs of retroperitoneal great vessels in patients with retroperitoneal tumors. METHODS We retrospectively analyzed imaging, surgical, treatment and survival data of all pediatric patients with retroperitoneal tumors who underwent resection between January 2007 and October 2016, comparing preoperative scans with corresponding intraoperative observations, and subsequent surgical outcomes. RESULTS Among 66 children with renal, adrenal and paravertebral tumors, 6 (9%) had retroperitoneal VIVAs. Retroperitoneal VIVAs were present only with right-sided tumors and significantly associated with more frequent intraoperative complications (P = 0.013). While the presence of retroperitoneal VIVAs was not directly associated with survival outcomes, relapse was more frequent in patients with VIVAs (33%) than those without (18.3%, P = 0.378), and relapse was also associated with lower overall and event-free survival (P < 0.001). CONCLUSIONS VIVAs of retroperitoneal great vessels occurred in 9% of our patients with retroperitoneal tumors. Retroperitoneal VIVAs were associated with higher rates of intraoperative complications and disease relapse but was not directly related to survival outcomes. TYPE OF STUDY Retrospective review study. LEVEL OF EVIDENCE Level III Retrospective comparative study.