In the practice of maxillofacial surgery, one major challenge is the correct reconstruction of malformed or damaged bone structures of the face. Among those, a rather frequent task is the remodeling of an injured orbit to be symmetrical to the intact one. Here, the main difficulty of this intervention is the necessity to plan the repositioning of bone fragments as to achieve symmetry. In this paper we present a computer-aided method for planning orbital reconstruction. A new software tool has been developed, which provides facilities for processing and displaying volume datasets. Moreover a symmetry plane in 3D can be defined using a specialized user interface. Based on this symmetry information, parts of the anatomy can then be highlighted and mirrored. This facilitates the comparison of structures in the two halves of the patient's face.