Statement of problem: different luting cements are selected to offer the retention of copy post for overdenture. The aim: This study was conducted to compare the effect of post length in the root canal on retention of posts cemented with various cements for overdenture abutment. Materials and Methods: extracted teeth were endodontically treated and were restored by metal copy post with different length and cemented by five different cement types. The Tensile strength (N) measured by Universal Testing Machine. Results: there was significantly differ between Fuji cement with zinc phosphate, poly carboxylate and glass ionomer cement in short copy post.  On other hand, there was significantly differ in long copy post among zinc phosphate, poly carboxylate and glass ionomer cement. Conclusions:It can be concluded that, the Fuji cement recorded highest retentive force with short copy posts, and zinc phosphate cement recorded highest retentive force with long copy posts