This work deals with seismic protection of steel building structures using hysteretic energy dissipators. The sensitivity of the performance of these systems to the design parameters of the dissipative devices is numerically investigated. Particularly, the influence of the vertical distribution of the yielding forces of the dissipators is deeply examined; two major approaches are compared. Comparison is established in terms of the response of a 15-story steel building subjected to the Lorca earthquake. Initial results seem to indicate little sensitivity of that response to the design yielding forces of the dissipators.