OBJECTIVE To validate the non-invasive tests that can predict the type of bladder dysfunction normally diagnosed by invasive urodynamics. METHODS Children below 12 yrs of age were evaluated prospectively. Non-invasive urodynamic evaluation included history, clinical examination, frequency volume charting, ultrasonographic scan, urine analysis and renal function tests. Micturating cystourethrogram was carried out in children with recurrent urinary tract infections. All children underwent invasive urodynamic studies and the significance of association of the parameters of noninvasive assessment with invasive urodynamics was determined. Chi square test using Epi 6 software was used for statistical analysis of data. RESULTS 41 children underwent invasive urodynamic studies. The commonest disorder was detrusor instability in 28 (68.2%). Dysynergic voiding was noted in 8 (19.5%). The study was normal in 5 (12.1%). Nocturnal enuresis with day time symptoms, holding maneuvers, small frequent voiding pattern (p<0.05) and a small capacity bladder with insignificant residue (p=0.0003) predicts detrusor instability. Straining (p=0.0006), large capacity bladder with significant post void residue in the absence of vesicouretric reflux (p<0.05) predicts dysyneric voiding. On combining the various non-invasive tests and validating them against invasive urodynamics in diagnosing detrusor instability and dysnergic voiding, they have a sensitivity of 88.4% and 87.5%, specificity of 72.7% and 69.2%, positive predictive value of 0.88 and 0.63 and positive likelihood ratio of 3.1 & 2.2 respectively. CONCLUSIONS Functional voiding disorders can be diagnosed with reasonable accuracy by minimally invasive methods.