The optimal timing of surgery is a balance between the risk of the lesion, the risk of surgery, the risk of age factors, and the level of perioperative management at each hospital. In general, the timing of surgery for ventricular defects is determined by the size and location of the defect, the size of the fractional flow, and whether secondary changes are combined. Small perimembranous ventricular defects of 4 or 5 mm or less have the potential to close on their own and can wait until around 6 years of age. Annual review is required. The ventricular defect with a slightly larger perimembranous ventricular defect but with a small fractional flow, such as about 6mm, and a small myocardial fraction, can wait until the age of 2-3 years, or until the weight of 10 kg or more. Ventricular defects under the stem, regardless of size, should be done early and are prone to secondary changes in the aortic valve, even if the fractional flow is not large. If there are no valvular problems, it is recommended to do it in 6-10 months. Large ventricular defects with large fractional flow can be done up to 6-8 months if there are no recurrent colds, pneumonia, no growth retardation, and no feeding difficulties.