With regard to structures design, we can divide structural optimization into three types: topology, shape and sizing. This work deals with the topological and sizing optimization, which can be considered at the conceptual and detailed design stages, respectively. The former refers to the optimization of a rear cabin suspension bracket, where the cost function is the structure compliance, which should be minimized, with a material volume restriction. The latter is regarding the optimization of a frame air filter bracket, being the objective function the material volume, which should also be minimized, subjected to a natural frequency restriction. Structural analyses are performed using the finite elements method.