Medical treatment is a therapeutic activity aimed at improving the patient’s health, but it is an invasive activity that involves risks to the patient's body and may unintentionally cause side effects or sequelae. Therefore, the patients consider seriously and decide whether to accept or refuse medical treatment based on the professional explanation of the doctor in charge of the medical treatment. However, this expectation is based on the assumption that the patient has sufficient capacity to understand the doctor’s explanation and make judgments, so it should be carefully examined whether the same treatment can be achieved in the case of someone who lacks capacity to understand and make judgments. The Supreme Court Decision 2020Da218925 delivered on March 9, 2023 decided that a minor patient with decision-making capacity can have the right to self-determination, so a doctor is obligated to explain medical treatment to a minor patient in principle, but such explanation may be recognized as fulfilling the doctor’s obligation of explanation by delivering the explanation to the minor through a parent or legal representative, or the doctor must explain medical treatment directly to the minor patient only if there are special circumstances, and this article reviews the reasoning and judgment of the Decision. The Decision is significant in that the Supreme Court has decided for the first time that, in principle, a doctor is obligated to explain medical treatment to a minor patient as long as the patient has decision-making capacity, even if the patient is a minor and in principle, a doctor may fulfill the duty of explanation to a minor patient by indirect explanation through a parent or legal representative, but there are exceptions to this principle, and the decision explicitly provides two types of examples of such cases. However, as long as a minor is recognized as having the same decision-making capacity as an adult patient, the direct explanation by the doctor to the minor patient, rather than the indirect explanation by the parent or legal representative, should be the principle method of fulfilling the duty of explanation, it would be more appropriate to allow indirect explanation to be permitted as an exception in cases where there are special circumstances that make such direct explanation difficult.