In this paper we present the evaluation of a virtual mirror used as a navigational tool within a medical augmented reality (AR) system for laparoscopy. 12 surgeons of our clinical partner participated in an experiment to evaluate whether laparoscope augmentation extended by a virtual mirror is useful for improved perception of complex structures. Such complex structures are encountered for instance in laparoscopic resection of tumor affected liver tissue. The blood vessels supplying the tumor have to be cut and closed before tumorous tissue can be removed. A laparoscopic camera and an optical tracking system allow for the visualization of visualized medical volumetric data registered with the real anatomy. Previously injected contrast agent provides an accentuation of blood vessels within the visualization. For evaluating the suitability of a virtual mirror to support the mentioned procedure, we designed a phantom consisting of wooden branches simulating the structure of blood vessel trees. Quantitative results of the experiment show the advantage of a mirror in certain cases, when blood vessels cannot be directly seen from the camera point of view due to self-occlusion of the structure. Results of a questionnaire filled out by the surgeons after the experiments confirm the acceptance of AR technology for particular medical procedures.