The synthesis, characterization and dielectric properties of rare earths substituted calcium manganese oxides [Ca2-xLnxMnO4, where Ln = Nd and Y] compounds were investigated. The dielectric properties of these compounds were studied in the frequency range from 20 Hz to 1 MHz between 20 K and 300 K. The low temperature dielectric properties is studied when x > 0.3 for Ln = Nd and Y. The activation energies increase as the amount of substitution x increase. Compounds for x > 0.3 are studied in dielectric permittivity, dissipation factor, activation energy with thermally activated process, modulus spectra, and cole-cole plot.