The AOC 15/50 wind turbine blade has been considered as the baseline configuration for a structural optimization process based on a multi-objective genetic algorithm. Through the optimization of several combinations of both the type and the layup of the laminas, an improved rotor blade has been obtained without changing the composite materials adopted for the original architecture. The design variables of the optimization are both the choice of the employed materials and their placement in the layout of the blade skin. A marked reduction of the overall blade weight and a corresponding increment of its flap-wise rigidity have been obtained. An unwanted small increase of the edgewise deformation has also been registered, requiring a further optimization process starting from the obtained optimal rotor blade configuration, in order to enhance also the edgewise rigidity of the blade.