A systematic study was carried out to explore the electrochemical behavior of Ce in room temperature ionic liquid (C_nmimBr, where n=6, 8, 10) and mixture of C6mimBr and ethanol by cyclic voltammetry. With increase in the number of carbon atoms on the alkyl substituent on methyl imidazolium cation, the electrochemical window of the ionic liquids was found to extend towards more negative potential value, as a result there was a possibility of reduction of Ce to lower oxidation states. The diffusion coefficient and activation energy for the diffusion were calculated in all the ionic liquids and one of their mixtures with ethanol. With increase in n value, the diffusion coefficient of Ce decreased due to increase in viscosity of the medium while the activation energy for the diffusion followed a reverse trend for C₆mimBr, C₈mimBr and C₁₀mimBr, respectively. The observations indicated that the nature of species of Ce might be different in room temperature ionic liquids (RTILs) from that present in their mixtures with ethanol.