Computer-navigated surgery Computer-navigated surgery has become very popular in the recent years. It provides "the third dimension" to CT scans and endoscopic images. This technique enables the surgeon to reach given structures in the operation field using instruments and to visualise their location on CT scans acquired earlier by the computer and presented on the screen. Computer-navigated surgery facilitates the visualisation of instruments position in relation to anatomical structures in three projections. Because of the simultaneous presentation of the scans and the endoscopic picture on one screen, enormous comfort is granted to both the surgeon and the patient who can feel safe. The analysis of images reveals further information, which enhance the safety and lead to more effective procedures with diminished complications. The surgeon's assurance that the instruments are in the desired position, even in the anatomically complex structures, is the most impressive advantage of this technique. Computer-navigated surgery can be of great benefit in endoscopic surgery teaching programs. However, it cannot become a substitute of an adequate knowledge or replace proper education about anatomy of operated organs. The authors present the review of systems for computer-navigated surgery. They also describe their own experience based on endoscopic surgery of ethmoid and maxillary sinuses carried out with the use of computer navigation.