The behavior of long span suspended bridges is influenced by different and complex aspects that need to be treated and evaluated deeply, organic and systematic. The Performance approach in the design process, strictly linked with the new philosophy of the Performance-based Design, allows a rational approach of the design problematic, with the possibility of optimizating the different parameters and levels of detail. To do that, it must be clear which are the peculiar aspects that the design of this typology of bridge must concern, above all referring to the geometrical non linearity of the system. Moreover, big attention must be paid in the realization of the main topics of the entire design process, represented by the structural modeling of the system, which allow to estimate realistically the structural response to the action that act during the exercise phase.