The liver is the largest odd parenchymal organ and the largest gland in the body, which on average accounts for about 5% of body weight in the newborn. It develops from the primitive gut, and her foundation appears mid third week as the projection of the endodermal epithelium at the distal end of the anterior intestine. It is the organ that performs many functions in the body, which, however, are not fully developed in the neonatal and childhood. One of them is the metabolism of drugs that are mainly carried out through two kinds of biochemical reactions (reaction phase I and II.). Specifically, children of different ages metabolize drugs differently. Drugs used in children to achieve anesthesia are the same as those that apply to adults. With development of pharmacological industry, anesthetic drugs with a number of unwanted side effects are replaced by new, more secure means for patients. For example, previously the most commonly used inhaled anesthetics halothane, because of its hepatotoxic effect, today is suppressed by using sevoflurane, which is considered the best inhaled anesthetics for use in children. However, there is no completely safe anesthetic. Even sevoflurane has been confirmed by numerous studies as a drug with detrimental effect to the liver, mainly in the form of a slight increase of aminotransferases. As well, there have been cases in which sevoflurane led to pronounced liver dysfunction and fulminant hepatic necrosis and hepatitis. At the present time, the target is to anesthetize small patient with technique and drugs that in the necessary and given time duration have less side effects.