Background: Nocturnal enuresis or bedwetting is the most common type of urinary incontinence in children. It has significant psychological effects on both the child and the family. The Aim of study was to evaluate the role of UDS in management of refractory Nocturnal Enuresis (MNE). Patients and Methods :This Prospective Study was carried out in Urology Department, Zagazig University Hospital that included 24 Patients, 14 boys and 10 girls. The patient ages was ranged from 10–18 years old with mean age (SD) of 11.91± 1.95 years. All patients were treated with mono pharmacotherapy (desmopressin). The duration of treatment before UDS at last six months. Results: bladder sensation was intact in 41.7%, increased in 50.0% and decreased in 8.3% of patients. The value of a single test PVR was ranged from 20-150 ml. 21 of patients were no post voiding volume (87.5%) and 3 cases had post voiding volume (12.5 %). The filling cystometry was normal in 6 patients (25%) and abnormal in 18 patients (75%). Bladder sensation intact in 10 patients (41.7%) and decrease in 2 patients (8.3%) and increase in 12 patients (50%) with p-value (< 0.05). conclusion: it is recommended to perform urodynamic studies in the form of uroflowmetry and cystometry for those with refractory nocturnal enuresis who failed ADHC ( desmopression ) for at last 6 months as initial monotherapy. Also a combination therapy of anticholinergics with desmopressin could be applied as treatment for those with refractory monosymptomatic nocturnal enuresis