A system to automate the design of passive filters using a multi-objective approach is presented on this work. A fixed but flexible structure is used to code the chromosome representing the circuit topology. An automated procedure is developed to size the circuit components from a given set of specifications. The novelty of this work is the multi-objective approach, where, for one side, priority is given to smaller circuits with less components, but, on the other side it must obey with the performance specifications. The ability of the proposed tool was tested on the design of several filter specifications.