Purpose: Cone beam computed tomography (CBCT) is increasingly overtaking multislice computed tomography (MSCT) for implant planning and computer-aided design/computer-assisted manufacturing (CAD/CAM) surgical guide fabrication. The purpose of this study was to evaluate whether the image modality has a significant influence on the accuracy of image-fusion stereolithographic guides. Materials and Methods: A total of 240 implants were placed in 30 polymer models using surgical guides fabricated using CBCT or MSCT and optical scanning of dental casts and diagnostic wax-up. Postsurgical image data were fused with the planning data for evaluation of the following errors: total error (Euclidean error), mesiodistal and buccolingual error, depth error, and angular error. The CBCT and MSCT results were statistically compared using a t test (P = .05). Results: CBCT showed a statistically significantly higher total error with mean (± SD) of 0.36 ± 0.13 mm vs 0.27 ± 0.13 mm (P = .000), mesiodistal error with 0.20 ± 0.14 mm vs 0.16 ± 0.11 mm (P = .018), and depth error with 0.17 ± 0.12 mm vs 0.07 ± 0.07 mm (P = .000). Buccolingual and angular errors did not statistically significantly differ with 0.16 ± 0.11 mm vs 0.15 ± 0.12 mm (P = .613), and 0.96 ± 0.47 degrees vs 0.85 ± 0.59 degrees (P = .111). Conclusion: Using CBCT for image-fusion stereolithographic guides may provide lower accuracy than MSCT. The results should be confirmed on alternative CBCT scanners. Due to the total volume of tissues, image artifacts, and patient movements, the advantages seen using MSCT on models could be nonexistent or exacerbated on patients. Patient studies are required to demonstrate clinical relevance. Keywords: 3D optical scanning, accuracy, cone beam computed tomography, multislice computed tomography, stereolithography, surgical guides