Abstract: Photoinduced electron transfet of aqueous and non-aqueous Cadmium Sulfide (CdS) dispersions in the presence of electron acceptors such as PQ⁺⁺ have been studied by means of ESR. The results show that upon irradiation of light (λ<517nm) the electron in the valence band (VB) of CdS can be excited to the conduction band (CB) giving rise to an electron-hole pair and the electron transfer from CB to PQ⁺⁺ to form free radical PQ⁺⁺ which can be detected by ESR.When electron donor such as EDTA is added to the systems, there is enhancement in the formation of PQ⁺⁺ which suggests that this hole is neutralized through the oxidation of EDTA.This returns the system to its original state thus allowing the CdS particles to be functional again in the photoproduction of PQ⁺⁺. Hence the CdS darticles are playing a catalytic role and in fact can be considered as a photocatalytic pump in which electrons are transfered from EDTA to PQ⁺⁺.