This　work　deals　with　the　multi-objective　optimization　of　single　Tuned　Mass　Dampers,　focusing　on　buildings　subject　to　low-moderate　earthquakes.　The　novelty　consists　in　considering　both　economic　and　performance　criteria.　The　economic　objective　is　represented　by　the　cost　of　the　device,　directly　related　to　its　mechanical　parameters,　while　the　ratio　between　the　absolute　acceleration　of　the　protected　structure　and　the　unprotected　one　is　assumed　as　performance　parameter.　This　latter　parameter　allows　in　fact　to　evaluate　the　damage　level　and　the　behavior　of　both　components　and　equipment.　A　multi-objective　optimization　problem　is　then　so　formulated　and　the　Non-dominated　Sorting　Genetic　Algorithm,　in　its　second　version,　is　applied　to　obtain　the　Pareto　optimum　solutions.　Finally,　by　a　sensitivity　analysis,　the　optimum　solutions　are　commented　with　respect　to　some　input　data.