Background:  children  with  congenital  heart  diseases have a  number  of risk  factors  for potential  development of  chronic kidney diseases later in  life such as :  including pathophysiological changes related to a structurally abnormal heart, polycythemia, cyanosis and chronic hypoxia change in renal blood flow and intraglomerular hemodynamics with derangements in neurohormonal activation. Objectives:this study aimed to assess renal functions in infants and children with congenital heart diseases and to compare renal functions between children with congenital cyanotic and acyanotic heart diseases.
 Patients and Methods: this across sectional case control study was carried out on 50 infants and children with congenital heart diseases (25 patients with congenital acyanotic heart diseases (Group A) and 25 with congenital cyanotic heart diseases (Group B) who were attended at the Pediatric Cardiology Units at Al-Azhar University Hospitals (El-Hussein and Bab El-Sheryia Hospitals) and apparently 25 healthy children age and sex matched included as a control group (Group C). Their age ranged from one month to 5 years old. Patients were subjected to full history taking, full medical examination which included the heart and abdomen and laboratory investigations which included complete blood picture, urine analysis, estimation of glomerular filtration rate, urinary albumin creatinine ratio. Data were collected, tabulated and statistically analyzed. Results:  comparing both groups A and B by group C as regards renal functions results; group B had higher values in all parameters (Estimated glomerular filtration rate (EGFR) and urinary albumin and creatinine ratio.
 Conclusion:  risk of renal dysfunctions increase by time especially in children with cyanotic CHD which may be due to effect of chronic hypoxia and other conditions such as polycythemia.