In this study, diagonal dominance of two input two output systems are discussed by considering the standard and weighted diagonal dominance conditions separately. In addition, sufficient conditions using static diagonal controllers are derived for fixed frequencies. Derived results can be easily extended for a given frequency range. An algorithm is proposed to determine static controller gain regions. Furthermore, by using the derived results, an optimization based method is proposed to determine dynamic diagonal controllers that achieve diagonal dominance conditions for static controllers. Lastly, case studies are included to verify the effectiveness of the proposed methods.