The optical and magneto-optical properties of evaporated Co1-xPtx alloys and Co/Pt mutilayers have been studied at room-temperature in the photon energy range 0.8 less-than-or-equal-to HBAR-omega less-than-or-equal-to 5eV. A maximum, Pt-induced Kerr rotation of \theta(K)\=0.66-degrees is found in evaporated alloys (x almost-equal-to 0.5) compared to \theta(K)\=0.49-degrees in corresponding multilayers. The difference is related to the type of Pt exchange polarization mechanism, which is 3D in alloys and 2D in multilayers, and a lower room-temperature magnetization due to a reduced Curie temperature in the multilayers. We confirm that a strong interband transitions at 4.2 eV due to Pt contributions is responsible for the remarkable Kerr effect in Co1-xPtx.