Treatment of deformities, diseases or traumas of the facial skeleton is very important for the functional and aesthetic importance of this structure. Craniofacial surgical techniques have had a great development during last decades. However, some problems still remain regarding the accurate repositioning of skeletal components and in defining margins in complex oncological resections. Computer technologies aid surgeons to solve these problems but most of proposed solutions are based on Virtual Reality. Virtual Reality technology provides many advantages but also the disadvantage that the surgeon has to adapt the virtual planning to the real surgical field. Augmented Reality represents the solution to this problem. We are developing an Augmented Reality platform for computer assisted surgery in the field of maxillo-facial surgery. In this paper we present the development of a surgical planning module that is integrated in this platform. The novelty is that this is the first Augmented Reality platform that includes such advanced planning module.