The intra-operative use of 3D-C-arm devices in the CMF operation theatre is becoming more and more popular. The advantages are particularly described for mid-facial and orbital reconstruction in which intra-operative scanning with 3D-C-arm devices can replace postoperative CBCT or MSCT. The aim of this study was the comparison of different types of 3D-X-ray machines concerning the applied equivalent dosage to the skull. We compared five devices: 64 slice MSCT; Siemens Somatom 3D-C-arm; Ziehm Vario-FD-3D 3D-C-arm; Siemens Iso-C-3D 3D-C-arm; Siemens Arcardis-Orbic-3D CBCT; Sirona Gallileos To determine the equivalent dosage of the devices in different locations, a phantom was loaded with ten dosimeters at the following anatomical regions: eye-lenses, optic-nerves, parotid-glands, submandibular-glands, hypophysis, sublingual-region. For simulation of clinical conditions, the depicted volume of all scans included the mid-face from the maxillary alveolar crest up to the upper frontal sinus. Comparison of MSCT vs. CBCT showed 4-times higher equivalent dosage for the MSCT. Comparison between C-arms of older generation (Vario-FD-3D, Iso-C-3D) and the MSCT showed 3- to 4-times higher equivalent dosage for the MSCT. The measured equivalent dosage of these two C-arm devices were almost similar to the CBCT. The C-arm Arcardis-Orbic showed a 10-times lower equivalent dosage in comparison to the CBCT and up to a 40-times lower equivalent dosage in comparison to the MSCT. The results show that use of intra-operative 3D-C-arm devices can significantly reduce applied radiation dosage compared to a post-operative MSCT. Using a C-arm device of a newer generation could even reduce the applied dosage significantly compared to dental CBCT-scans. Keywords: intraoperative imaging, MSCT, dental-CBCT, 3D-C-arm, computer-assisted surgery, radiation dose