Dentists have been using CAD/CAM technology to fabricate custom posts and cores. However, most of these cases used impression material as a way to indirectly scan the canal. The aim of this study was to evaluate the capability of CEREC CAM/CAM machine to directly scan simulated canal blocks without an impression and which of the following factors affected the accuracy of fit; taper, length and tip diameter. Material and methods: 32 epoxy resin blocks with post space simulator were made from metal post templates to resemble post space preparations. Three factors were considered in-group variations; length of the post, taper and diameter of the post’s tip. Eight groups of four specimens each were milled from acrylic blocks using the CEREC CAD/CAM system and one extra group of one specimen each was for cast post fabrication. Group A (Length = 8mm, taper = 4o, tip diameter = 0.8mm), Group B (Length = 8mm, taper = 4o, tip diameter = 1 mm), Grope C (Length = 8mm, taper = 6o, tip diameter = 0.8mm), Group D (Length = 8mm, taper = 6o, tip diameter = 1 mm), Group E (Length = 10 mm, taper = 4o, tip diameter = 0.8mm), Group F (Length = 10 mm, taper = 4o, tip diameter = 1 mm), Grope G (Length = 10mm, taper = 6o, tip diameter = 0.8mm), Group H (Length = 10mm, taper = 6o, tip diameter = 1mm). Each block, with its cemented post was sectioned in a coronal-apical direction. An image was recorded for each slice. Cement thicknesses were measured in four areas. The results showed that group E and D have the smallest cement thickness with 84 and 89 microns respectively. Both groups shared a tip diameter of 1mm. This result is within the clinically acceptable limit of the cement layer around the posts and is comparable to the cast group in our study. Tip diameter and length significantly affected the cement thickness in an inverse relationship.