1. This study was conducted to determine the effects of enzyme supplementation of maize/wheat-based diets on the performance, egg quality, and serum and bone parameters of laying hens.2. During the 12-week experimental period, a total of 72 laying hens aged 52weeks were randomly distributed among 6 experimental groups. Each experimental group contained 4 replicates, each with three birds. The experiment was a randomised design consisting of a 3x2 factorial arrangement, with three levels of wheat substitution and two levels of enzyme (xylanase: 1500.00U/kg, -glucanase: 100 000U/kg, cellulase: 1 000 000U/kg, -amylase: 160 000U/kg) inclusion in the diet. Wheat replaced 0, 50, or 100% of maize with or without 1.0g/kg enzyme supplementation in iso-nitrogenous and iso-caloric experimental diets.3. Body weight, egg production, egg weight, egg mass, eggshell thickness, and the feed conversion ratio were adversely affected by the wheat-based diet. The eggshell quality parameters decreased with enzyme supplementation to the diet.4. Wheat-based diets adversely affected calcium and phosphorus concentrations in the tibia, but the addition of the enzymes to the wheat-based diet prevented the negative effects of wheat-based diets on tibia mineralisation in laying hens. The wheat-based diets tended to reduce plasma mineral contents, and the addition of enzymes tended to affect plasma minerals and biomechanical properties of the tibia positively in laying hens.5. These results indicate that wheat-based diets in aged laying hens adversely affected the mineral metabolism compared with maize-based diets, and the negative effects of wheat on bone mineralisation can be prevented by enzyme supplementation to the diets in laying hens.