Objective: The aim of this study was to determine the erbium-doped yttrium aluminum garnet (Er:YAG) laser transmission ratio through different dental ceramics with different thicknesses. Background data: Laser debonding procedure of adhesively luted all-ceramic restorations is based on the transmission of laser energy through the ceramic and the ablation of resin cement, because of the transmitted laser energy. Methods: Five different dental ceramics were evaluated in this study: sintered zirconium-oxide core ceramic, monolithic zirconium-oxide ceramic, feldspathic ceramic, leucite-reinforced glass ceramic, and lithium disilicate-reinforced glass ceramic. Two ceramic discs with different thicknesses (0.5 and 1mm) were fabricated for each group. Ceramic discs were placed between the sensor membrane of the laser power meter and the tip of the contact handpiece of an Er:YAG laser device with the aid of a custom- made acrylic holder. The transmission ratio of Er:YAG laser energy (500mJ, 2Hz, 1W, 1000s) through different ceramic discs was measured with the power meter. Ten measurements were made for each group and the results were analyzed with two way analysis of variance (ANOVA) and Tukey honestly significant difference (HSD) tests. Results: The highest transmission ratio was determined for lithium disilicate-reinforced ceramic with 0.5mm thickness (88%) and the lowest was determined for feldspathic ceramic with 1mm thickness (44%). The differences among the different ceramics and between the different thicknesses were significant (p<0.05). Conclusions: Ceramic type and thickness should be taken into consideration to adjust the laser irradiation parameters during laser debonding of adhesively luted all-ceramic restorations.