In the vast majority of cases, precise symmetric reconstruction of maxillofacial defects remains an unsolved problem for craniofacial surgeons. Computer-designed alloplastic implants have contributed considerably to improvement in the accuracy and reliability of facial rehabilitation, rapidly becoming an irreplaceable part of the surgical armamentarium. In recent years, the subsequently developed new generation of computational technologies has allowed planning to be done by preoperative "mirroring" using the healthy side as a template to fabricate an ideal prosthesis for reestablishment of facial symmetry. Two cases of facial defects are reported, one of the midface and another of the lower face reconstructed using a computer-designed polyetheretherketone (PEEK) patient-specific implant (PSI) technique based on "mirroring" computational planning. LEVEL OF EVIDENCE V: This journal requires that authors assign a level of evidence to each article. For a full description of these Evidence-Based Medicine ratings, please refer to the Table of Contents or the online Instructions to Authors at www.springer.com/00266.