In previous work, we studied the electronic structure of several molybdate and tungstate crystals having the scheelite structure. The wolframite structure is another common form for molybdate and tungstate materials. In this paper, we compare two chemically similar materials which naturally form in the scheelite and wolframite structures -- CdMoO_4 and CdWO_4, respectively. Within the framework of density functional theory, we compare the electronic structure and approximate optical properties of these materials.