summary  This study evaluates the light‐attenuating effects of enamel on the properties of light‐cured restorative resins using simple experimental filters. Three filters were designed to replicate the light transmittance characteristics of 0·5, 1·0 and 1·5 mm thick human enamel. The bending strength, depth of cure, and levels of residual monomer for 12 shades of three commercial light‐cured composite resins were examined. These resins were cured either using direct irradiation from a light source or irradiation through one of the filters. For all materials, the bending strength and depth of cure of specimens irradiated through a filter were lower and the levels of residual monomer were higher than those found in specimens irradiated directly. The results indicate that the light‐attenuating effect of enamel reduces the polymerization efficiency, resulting in poorer mechanical properties of light‐cured composite resins.