We evaluate the dual cone of the set of diagonally dominant matrices (resp., scaled diagonally dominant matrices), namely DD * n (resp., SDD * n ), as an approximation of the semidefinite cone. Using the measure proposed by Blekherman et al. ( 2020) called norm normalized distance, we prove that the norm normalized distance between a set S and the semidefinite cone has the same value whenever SDD * n ⊆ S ⊆ DD * n . This implies that the norm normalized distance is not a sufficient measure to evaluate these approximations. As a new measure to compensate for the weakness of that distance, we propose a new distance, called trace normalized distance. We prove that the trace normalized distance between DD * n and S n + has a different value from the one between SDD * n and S n + , and give the exact values of these distances.