The electrochemical behavior of samarium (Sm), europium (Eu), and ytterbium (Yb) was investigated in the hydrophobic room-temperature molten salts based on bis(trifluoromethylsulfonyl)imide combined with either 1-ethyl-3-methylimidazolium or 1--butyl-1-methylpyrrolidinium . The redox reactions of , , and were observed at , , and vs , respectively. In all cases, the electrode reactions were found to be quasi- or irreversible by the cyclic voltammetry. The diffusion coefficients of these lanthanides were estimated to be by chronoamperometry and chronopotentiometry, indicating that their mobility is rather low, probably due to the complex formation or the strong coulombic interaction with . The redox potentials of these divalent and trivalent lanthanide couples suggested that the donor property of -based room-temperature molten salts was lower than that of other conventional solvents.