Objective: The aim of this study was to assess:1-The effect of surface treatments on zirconia core structure. 2- The validity of a new technique (Selective Infiltration Etching) to improve shear bond strength between zirconia core and the veneering ceramic.3- The influence of different veneering techniques on the core-veneer shear bond strength. Material and methods: Forty eight Zirconia partially stabilized Y-TZP discs (19 mm in diameter x 2.5 mm thick) were prepared out of Cercon Y-TZP milling blocks. Six Cercon Zirconia blocks were used to obtain the 48 discs using a precision cutting instrument and a diamond-coated cutting disc.The location of the cuts was controlled using a traveling stage and a horizontally displaced digital micrometer.The discs were divided into 3 main groups according to surface treatment; 16 discs in each group. Group1: Received no surface treatment and was left as sintered.Group 2: Airborne particle abraded (sandblasted). Group 3: Received SIE surface treatment.After surface treatment each main group was further sub-divided into 2 sub-groups according to the veneering technique, 8 discs each. Results: The results obtained showed that the Selective infiltration etching (SIE) group in interaction with the press - on veneering technique showed the statistically significantly highest mean Shear bond strength value. This was followed by(Sandblasting/layering),(Sandblasting/press–on)(Assintered/press–on)and(Assintered/layering) with no statistically significant difference between the four groups. The statistically significantly lowest mean microshear bond strength was recorded with (SIE/layering). Conclusions: Within the limitations of this study the following conclusions can be drawn: 1-Surface treatment of zirconia core has an influential role on its bond strength with the veneering material. 2-Press-on veneering technique is a more reliable veneering technique than the manual layering in respect to the core-veneer bond strength. 3-Selective Infiltration Etching (SIE) is not an effective surface treatment when used with the layering veneering technique. 4-Selective Infiltration Etching (SIE) surface treatment proved to be effective when used with the press-on technique. 5-Proper selection of zirconia framework surface treatment and matching veneering application technique is of extreme importance to guarantee acceptable clinical performance.