Objective: The aim of this study is to evaluate the effects of thickness increase in nanohybrid and microhybrid composites on translucency, opalescence and masking efficacy. Material and methods: For this study, a total of 72 composite discs with thicknesses of 1, 1.5 and 2 mm were prepared from nanohybrid and microhybrid composites. Disk measurements were made with the aid of a spectrophotometer and translucency parameter (TP), opalescence (OP-BW) and masking efficacy (ME) were calculated. Results: The decrease in the values of TP and OP-BW and increase in the values of ME were observed with thickness increase in both microhybrid and nanohybrid composites. Moreover, while statistically significant positive correlation was detected between TP and OP-BW, it was also detected that ME and TP and ME and OP-BW were statistically significant between each other but negative correlation was detected. Discussion: The thickness of composite materials directly affects the aesthetic properties of restorative materials.