The purpose of this article was to evaluate function of lower urinary tract for 5-18 years old children with recurrent urinary tract infections and to compare urodynamic changes in two groups: with recurrent lower urinary tract infections and with recurrent upper urinary tract infections. 35 urodynamic studies in 5-18 years old children (3 boys and 32 girls) with recurrent urinary tract infection were performed at the Clinic of Children's Diseases of Kaunas University of Medicine in 2004. 21 of these children had recurrent lower urinary tract infections and 14 recurrent upper urinary tract infections. Changes in urodynamics were present in 91.4% of children: in all children with recurrent lower urinary tract infections and in 11 children with upper recurrent urinary tract infections (78.6%). Detrusor instability was found in 20 (57.1%) children: in 14 (66,7%) with recurrent lower urinary tract infections and in 6 (42.9%) with recurrent upper urinary tract infections. In 32 (85%) children detrusor instability was accompanied by changes in bladder volume. Changes of bladder volume were present for 26 (74.3%) children with recurrent urinary tract infections. Detrusor after contraction was diagnosed in 57.1% of children with recurrent lower urinary tract infections and in 28.6% with recurrent upper urinary tract infections. For children with recurrent urinary tract infections attention for urinary tract dysfunction must be paid.