Background: Traditionally the procedure of percutaneous ASD closure is carried out in children weighing more than 15 kg. The aim of this study was to discuss the success, efficacy and safety of the percutaneous closure of symptomatic ASD in children weighing less than 10 kg. Material and methods: This study was performed in two centres. A total of 44 patients were included. Demographic and angiographic data of these patients were gathered retrospectively from patients' records. Main indications for ASD closure were: failure to thrive, recurrent respiratory infections, bronchopulmonary dysplasia and genetic syndromes. Results: Median weight of patients was 9.0(8.12-9.50) kg. Bodyweight of 22 patients was less than 3 percentiles. In the follow-up, this number was lowered to 9 patients at 12 months. Median age of patients was 18.0(12.0-285) months. Minimum age and weight of patients was 3 months and 4.5 kg, respectively. Median mean pulmonary pressure was 24.0(20.0-29.5). The values of median defect size were measured in Cath lab as 13.0(10.75-15.3) mm. Median device size was 13(9-15) mm. Defect size was evaluated according to body weight and body surface area. The ratio of weight per defect size was 0.65(0.54-0.84) also the ratio of body surface area per defect size was 0.032(0.028-0.04). The ratio of total septum per device diameter was 2.5(2.1-3.1). Types of devices used were Amplatzer Septal Occluder, Cera Flex Septal Occluder, Figulla Flex II Atrial Septal Occluder, Memopart Septal Occluder. All cases were closed successfully, but the device had to be retrieved in one patient after successful positioning because it was detected that device compressed the aorta. No major complications were seen. Conclusion: In the experienced centres, percutaneous ASD closure can be done effectively and safely in symptomatic children weighing less than 10 kg.