Background: A ureteropelvic junction (UPJ) obstruction is a congenital anomaly commonly afflicting the pediatric population. However, it occurs more frequently in adults than is generally appreciated. To assess their characteristics, we have here compared and analyzed the clinical manifestations, causes, and outcomes of UPJ obstruction found in children and adults. Materials and Methods: 102 patients (118 renal units) out of 182 patients (218 renal units), with diagnosed UPJ obstruction, were available for follow up. The follow-ups were retrospectively reviewed to determine the presenting symptoms, treatments, and clinical outcomes. Patients who were younger than 18 years of age were assigned to the pediatric group (44 patients), others the adult group (58 patents). Results: The majority of the patients presented with flank pain (pediatric group: 68%, adult group: 76%). The majority of patients underwent a pyeloplasty (pediatric group: 50.9%, adult group: 62.3%). And the major cause of the UPJ obstruction was an intrinsic stenosis (pediatric group: 53%, adult group: 56%). Conclusion: The prevalence of bilateral UPJ obstruction in adults is evidently less prevalent than in pediatrics, and despite the late diagnosis, the surgical outcome is similar. A further investigation of UPJ obstruction will lead us to a more comprehensive understanding of the disease.