Purpose: Patient-specific implants (PSIs) and surgical guides are widely used nowadays for the reconstruction of craniofacial defects. In this research, we quantitatively compared the realised position of craniofacial PSIs with the planned position and we calculated the difference between the realised osteotomy and the planned osteotomy if a resection preceded the reconstruction. Methods: We retrospectively included patients who received a craniofacial polyetheretherketone (PEEK) PSI in the LUMC between February 2019 and January 2021 and had a postoperative CT scan available. Postoperative CT scans were aligned with preoperative CT scans, followed by segmentation of the postoperative PSI position and skull, on which the realised osteotomy was defined by an inner and outer curve. Translation and rotation between the realised PSI position and planned PSI position were calculated as well as the surface distance between the realised osteotomy curves and the planned osteotomy. Results: 19 patients were included, regarding cranial (n = 11) and orbital (n = 8) implants. The translation vector length ranged from 0.5 mm to 6.7 mm and rotational deviation ranged from 0.9° to 17.4°, both being higher for orbital implants than for cranial implants (U = 3.00, p = .000, U = 15.0, p = .016). 12 patients were included in the osteotomy analysis. Mean distance between realised and planned osteotomy was 1.4 mm (SD 1.6) for outer curves and 0.5 mm (SD 1.7) for inner curves. Absolute mean distances over the two curves ranged from 0.6 mm (SD 0.5) to 4.1 mm (SD 2.6), accurately reproducing the planned osteotomy in most cases. Conclusion: In this study, there was a large variation in positioning accuracy for craniofacial PSIs. Cranial implants, being in good agreement with the planned PSI positions, were positioned with higher accuracy than orbital implants. In general, realised osteotomies were larger than planned. Better use and positioning of surgical guides could increase the PSI positioning accuracy. Clinical and aesthetical outcomes need to be included in future studies.