Abstract — This article presents experimental studies comparing trajectories obtained from the movements of a medical instrument by a surgeon and the robot KUKA LWR4 +. The comparison is made according to one of the four main criteria – standard deviation from the average cutting velocity. Such metrological studies are a method of justifying the expediency of using a robot for medical operations. This criterion can be used to compare trajectories when performing medical operations in maxillofacial surgery using a diode laser. The presented comparison criterion is based on the ISO 9283 standard. In addition to the main criterion, there are 2 additional ones. The trajectories for comparison were obtained by scanning the movements of a medical instrument using a coordinate measuring machine - the laser tracker LTD800. With the use of a robot, it is possible to achieve higher accuracy of trajectories by the velocity of movement of the medical instrument in comparison with a surgeon.