Objective To evaluate the clinical effect of balloon dilatation in the treatment of lower urinary tract obstruction in children. Methods Twenty-six boys suffering from lower urinary tract obstruction underwent the balloon dilatation operation. These patients included 23 cases of posterior urethral valves, 2 cases of anterior urethral valves and 1 case of traumatic urinary tract stricture. Their ages ranged from 18 days to 7 years. All the patients were diagnosed by voiding cystourethrogram (VCG). Some of the boys suffered from bilateral hydronephrosis and dilated ureters. Before operation, the patients with urine retention or abnormal renal function should drain urine and correct the disorderof fluid and electrolyte. Balloon dilatation was done after their conditions were improved. During operation, ketamine anaesthesia was used, and 30% diatrizoate melglumine was used as dilatation drug. The balloon catheters which had the length of 4 cm and the diameters of 5，8，10 mm respectively were used for dilating the urethra. After operation, a Foley’s catheter was routinely indwelled. Results During procedure, compression phenomena disappeared in the course of operation. All the patients urinated normally after catheter was removed at 1 week post operatively. 6 cases received ureteral reimplantation to prevent vesioureteral reflux after 1 to 3 months. 25patients were followed up from 1 to 13 years and all patients had normal micturition and the bilateral hydronephrosis were improved. Conclusion Balloon dilatation is a safe, effective and feasible therapy for lower urinary tract obstruction in children.