Objective: Congenital heart diseases in childhood are an important cause of morbidity and mortality. The frequency of non-cardiac anomalies in children with congenital heart diseases is between 7-50%. Urinary system anomalies are an important risk factor in children with congenital heart diseases. The aim of this study was to evaluate the presence, types and frequency of urinary system anomalies detected during cardiac catheterization in children with congenital heart diseases. Methods: The cineurography records of 6000 patients who underwent cardiac catheterization due to congenital heart diseases were retrospectively analyzed. Urinary system anomalies detected were examined as renal agenesis, renal ectopia, renal fusion, dysplastic kidney, obstructive uropathy, vesicoureteral reflux, ureter anomaly and bladder anomaly. Patients were grouped as right ventricular outflow tract obstruction, left ventricular outflow tract obstruction, left-to-right shunted hearth disease and, cyanotic or complex heart diseases. The groups were compared in terms of urinary system anomaly types. Results: Seventy-six patients (47 male and 29 female) with urinary system abnormalities were detected. Obstructive uropathy was found in 43 (56.5%) patients, renal agenesis was found in 14 (18.4%) patients, ureter anomaly was found in 14 (18.4%) patients, renal fusion was found in 3 (3.9%) patients, renal ectopia was found 1 (1.3%) patient, vesicoureteral reflux was found in 1 (1.3%) patient. There was no significant difference in term of the urinary system anomaly types among the groups (p>0.05) Conclusion: Urinary system anomalies may also be frequently accompanied in children with congenital heart diseases, so urinary system should also be evaluated during the cardiac catheterization procedure.