Since electromagnetic bandgap (EBG) structures reduce power-bus noise effectively, they are prospective for overcoming the intra electromagnetic compatibility (EMC) issues in wireless communications. A vialess open-stub EBG structure we have previously proposed can be designed with only two layers of power and ground planes, and the lower-end frequency of the stopband can be determined easily by setting the stub length. However, it is difficult to determine three structural parameters of the vialess open-stub EBG structure, stub width, branch width, and unit-cell length, so that a wide stopband and large attenuation are simultaneously satisfied. Thus, this paper aims to optimize the structural parameters by applying a multi-objective satisfactory design method, Preference Set-Based Design (PSD), to the vialess open-stub EBG structure. As a result, we obtained the ranges of three structural parameters satisfying the required performances.