ABSTRACT Purpose: Posterior urethral valves (PUVs) are the most common cause of congenital bladder obstruction in boys. Our aim was to assess the impact of early diagnosis and fulguration of PUVs on bladder function and compare their functional and urodynamic outcome with children who underwent delayed intervention. Materials and Methods: We retrospectively evaluated 153 patients who underwent primary valve ablation from two tertiary hospitals between 2001 and 2018. Patients have been divided into 2 groups, group 1 included 69 patients who were detected antenatally and underwent early fulguration of PUVs while group 2 included 84 children presented postnatally and underwent delayed valve ablation. The recorded data throughout follow-up in renal function tests, urodynamics and changes in the upper urinary tracts were evaluated and compared. Results: Median age at time of valve ablation was 10 days in group 1 and 7 months in group 2. The median follow-up period was 6.5 and 7 years in group 1 and 2, respectively. Chronic kidney disease (CKD) developed in 15 (22%) boys in group 1 while in group 2 it was observed in 31 (37%), p=0.04. While Q-max, mean bladder capacity and post-void residual (PVR) volumes were comparable in both groups, percent PVR was significantly higher in group 2 (3.27 vs. 1.44, p=0.002). Detrusor overactivity was slightly different in both groups (p = 0.07). Conclusions: Compared to delayed intervention, primary ablation of PUVs during the early neonatal life possibly provides the optimum chance to have optimum renal function without impact on bladder function.