Objects: Approximately, 1% of school children have daytime urinary incontinence. The symptoms may be caused by an overactive bladder (OAB). In the evaluation of boys with OAB complaints, one should consider a possible urethral cause. The aim of the study was to evaluate the value of a diagnostic regime with cystourethroscopy, voiding cystourethrography (VCUG) and urodynamic pressure-flow studies in boys with OAB complaints after unsuccessful urotherapy and pharmacological therapy. Materials and Methods: Seventy-five boys (5-14 years old) were investigated with cystourethroscopy and within 24 h thereafter VCUG followed by urodynamic combined cystometry and pressure-flow study. All boys had daytime incontinence and urgency. Results: Sixty-one boys had no suspected urethral valves at cystoscopy or VCUG, and urodynamics showed no obstructed Pdet-Qmax. All 61 boys had detrusor overactivity. Two boys had late diagnosed urethral valves. In four boys, the initial cystourethroscopy was described as normal. The VCUG indicated presence of posterior urethral valves, but urodynamics showed no obstructed Pdet-Qmax. In eight boys, the initial cystourethroscopy was described as normal whereas urodynamics showed obstructed Pdet-Qmax. In four of these boys, VCUG showed abnormalities in the sphincter area but they were not described as suspected urethral valves. At repeat cystourethroscopy, urethral valves could still not be identified. Patient follow-up regarding achievement of continence after investigation guided treatment was in accordance with the literature. Conclusions: Boys can be safely evaluated by cystourethroscopy followed by urodynamics in search for a possible urethral problem. It is our suggestion, that VCUG can be restricted to those boys where urodynamics indicates obstruction or the findings by cystourethroscopy are uncertain.