[en] Separation of light lanthanoids with centrifugal partition chromatography (CPC) was investigated in extraction system of 30% HDEHP/CCl₄/n-paraffin and HNO₃. Since separation factors between lanthanoids, Ce, Nd, Pr, Sm, Eu and Gd, were independent of volume ratio of CCl₄ and n-paraffin diluents, difference in the density between the mobile phase and the stationary phase was controlled by varying the volume ratio of two diluents in order to operate at reasonable pump-pressure. The effects of volume of the stationary phase and rotational speed on the separation characteristics of CPC were examined to find the optimum operation conditions. The effect of chain length of n-paraffin (number of carbon atoms: 6--15) as diluents was also examined. The best separation efficiency was obtained with the longest, n-pentadecane. On the basis of the above results, mutual separation of lanthanoids was successfully performed in 30% HDEHP/15% CCl₄/55% n-pentadecane and 0.5 mol/dm³ HNO₃ extraction system at a low pump pressure of 4.5 kgf/cm²