Statement of problem:Surface treatment of reinforced fiber posts may not always increase adhesion, especially on post/resin based luting agent interface which is weaker than the dentin/adhesive interface. Relatively little information is available on cone beam computed tomography as non-destructive method suitable for investigating the details of the tooth structure and restoration relationship. Purpose: The purpose of this study was performed to evaluate porosities and gaps at post/ root dentin interface by CBCT and correlate them to push out bond strength of conventional and reinforced glass fiber posts after different surface treatments; hydrofluoric acid, hydrogen peroxide and sandblasting. Materials and Methods: Forty human maxillary central incisors were selected, decoronated to set the remaining tooth length to standardized length of 13mm from the root apex and endodontically treated. The prepared roots were randomly divided into 2 fiber post groups(20 per each). Group 1: white posts DC were selected. Group 2: easy-posts TM were selected. Within each group, posts were further subdivided into 4 subgroups (5 per each) according to surface treatments of the posts. Subgroup A: no treatment, the posts acting as control group. Subgroup B: etching by 9% buffered hydrofluoric acid for 1 minute and bonding. Subgroup C: immersion in 20% H2O2 for 15 minutes and double application of silane for 1 minute per each application. Subgroup D: sandblasting by alumina particles and silainization for 1 minute. Posts were cemented inside roots using Duo-link Universal TM resin cement. Samples were examined by CBCT scans to evaluate voids and porosities. The CBCT scans of intra canal posts were measured in the axial plane. All measurements were made at cervical and middle slices in the buccal, lingual, mesial & distal directions. Each specimen was transversely sectioned perpendicular to the long axis of the root to obtain a section 2 mm ± 0.1 in thickness from the root thirds as measured using a digital caliper. Each section was coded and photographed from apical and coronal surfaces using a stereomicroscope.. Three-way analysis of variance ANOVA test of significance was done comparing variables (post, surface treatment and radicular region) affecting mean values. One way ANOVA followed by Tukey's post-hoc test was performed porosities and gaps at post/ root dentin interface by CBCT and correlate them to push out bond strength of conventional and reinforced glass fiber posts after different surface treatments were confirmed.. AL-AZHAR