Summary Purpose Posterior urethral valves (PUV) diagnosed during childhood have classically been associated with a better outcome than antenatally diagnosed PUV. The aim of our study was to compare long-term outcome of these two patients’ groups. Material and methods We retrospectively reviewed the medical records of boys with PUV managed between 1990 and 2010. Patient demographics, clinical background, radiographic data (including prenatal ultrasonography data when available), renal and bladder functional outcomes, surgical procedures and urinary tract infections (UTI) were abstracted. Impaired renal function (IRF) was defined as glomerular filtration rate less than 90mL/min/1.73m2 at last follow-up. Results We identified 69 patients with confirmed PUV. Thirty-eight were diagnosed prenatally (group 1) at 30.5weeks of gestation and 31 had a delayed diagnosis (group 2) at a median age of 6.31years. At diagnosis, 20 patients in group 1 had renal insufficiency versus two in group 2 (P<0.05). At the end of mean follow-up of 7.2±0.5years, in group 1, 26.3% developed IRF versus 6.3% in group 2 (mean follow-up 2.3years). Mean age at last follow-up was 7.3years in group 1 versus 8.3 in group 2 (P>0.05). In group 1, 27% had voiding dysfunction versus 30% in group 2 (NS). In group 1, 35% had UTI during follow-up versus 10% (P=0.01). Conclusion During the follow-up, the patients with delayed diagnosis VUP have developed fewer complications related to the initial obstruction than the population who was detected antenatally and managed from the early hours of life. However, the rate of IRF and voiding disorders in our study, associated with the data of the literature, highlights the potential persistence and worsening of these conditions. That is why, whatever the age at diagnosis, VUP patients require a close monitoring.