Aim: The aim of this study was to evaluate the fracture resistance of endodontically treated teeth with different amount of coronal dentin restored with ceramic post. Materials and Methods: Forty intact mandibular premolar were endodontically treated and decoronated horizontally 3 mm to most apical point of the labial cement-enamel junction. Teeth were divided into four groups Group I: Teeth prepared with retained four axial walls (control group). Group II: Teeth prepared with removal of mesial axial wall. Group III: Teeth prepared with removal of mesial and distal axial wall. Group IV: Teeth prepared with removal of mesial, distal, and buccal axial wall. All teeth were restored with cera posts and composite cores. All samples were tested using a universal testing achine at crosshead speed of 1 / in at 45˚ angle until failure. Results: the core materials revealed significant (p<0.05) influence of the (Composan > posite) on fracture resistance mean values, and the remaining wall showed non-significant(p>0.05) influence on the fracture resistance mean values(group II> group III> group IV).The interaction between(core x remaining wall) was statistically non-significant(p>0.05).Conclusion: Teeth restored with light cured packable composite (Composan ceram) had a significant higher fracture resistance than dual cured flowable composite (Corposite). The remaining coronal tooth structure did not have significant effect on the fracture resistance of endodontically treated teeth restored with prefabricated post and core material.