OBJECTIVES: The aim of this study was to evaluate translucency of zirconia lithium silicate and lithium disilicate glass ceramic with different thicknesses, pre and post cementation. MATERIALS AND METHODS: A 120 Specimens of the current study were fabricated out of the two tested materials each counting N=60, A1 (translucent) shades of zirconia-reinforced lithium silicate glass ceramic (ZLS, Vita Suprinity, Vita Zahnfabrik, Germany) and A1(translucent) lithium disilicate glass ceramics (Rosetta SM, Korea). Specimens had a uniform rectangular shape with standard dimensions of 15 mm length and 10 mm width. Specimens of each material groups were distributed into three main groups based of specimen's thickness 0.5mm, 1mm, 1.5mm each of these groups were further distributed into two subgroups based on translucency testing timing before or after cementation each counting 10 specimens. Specimens were fabricated by sectioning the ceramic blocks using a precision saw (IsoMet 4000, Buehler) under copious water coolant. Specimens final dimensions were confirmed with digital caliper. SPECTRO UV-Vis-Double BEAM spectrophotometer with an integrating sphere was used to evaluate the total transmittance of light as a percentage (T_t%) at a wavelength of 532 nm for comparison among groups. RESULTS: In the present study, translucency values at 0.5mm and 1 mm thicknesses LDS were higher than those recorded for ZLS at the same thicknesses. While with 1.5 mm thick specimens the translucencies of both ZLS and LDS materials were fairly similar. CONCLUSIONS: From the outcome of the current study, the following conclusions could be drawn out 1. The thinner the ceramic veneering layer, the greater will be the impact of the underlying shade on the final shade of the restoration. 2. The translucency values recorded for the translucent zirconia materials were not only almost close to those of the lithium disilicate ceramic material, but also comparable to the translucency values reported for enamel or dentin of similar thicknesses.