Efficient charge separation has been observed in blends of conjugated polymers and cadmium selenide nanocrystals. These composites, which can be used for photovoltaic applications, provide a unique medium for examining charge separation because the energy levels of both components can be tuned independently: those of the polymer by its side groups, and those of the nanocrystals by size-dependent quantum confinement effects. Here we study charge separation in such blends via photoluminescence quenching and photo-induced absorption measurements. The effects of polymer derivatization and nanocrystal size are investigated.