Cardiac output (CO) measurement is becoming increasingly important in the field of pediatric intensive care medicine and pediatric anesthesia. In the past few decades, various new technologies have been developed for the measurement of CO. Some of these methods are applicable to pediatric patients and some are already being used in children. The devices and methods have their advantages and limitations and, therefore, it is difficult for the clinician to decide which technique should be used. This article focuses on the currently available minimally invasive and noninvasive monitoring devices for CO measurement in children. A brief explanation of the technical aspects of each method and clinical use will be followed by the knowledge gained from infant animal and clinical pediatric studies. The goal of this article is to give an update of the various CO measurement technologies in children.