The purposes of the study were a) to assess the incidence of urinary system malformations in children with the nephrotic syndrome (NS) and b) to estimate their effect on clinical course of the NS. A retrospective analysis comprised medical records of patients aged 2-18 years hospitalized in the Department of Pediatric Nephrology, University Children's Hospital, Lublin. Urinary tract infections (UTI) occurred in 28% of children with the NS. Imaging evaluation revealed urinary system malformations in 21.2% of children with the NS and UTI. Urinary system malformations constituted 5.9% of all children hospitalized because of the NS. Urinary system malformations included vesico-ureteral reflux (42.8%), renal duplication (28.6%), renal agenesis (14.3%) and diverticulum of the bladder (14.3%). In 48% of children with the NS and urinary system malformations, frequent recurrences of the syndrome were observed.