Generalized Relativistic Effective Core Potentials (GRECPs) for lanthanides have been constructed where the 28 innercore 1s²2s²2p⁶3s²3p⁶3d¹⁰ electrons were excluded from the following GRECP calculations. Incorporation of Breit interactions in the GRECP operator has been illustrated on the example of the Sm atom. Atomic test calculations have demonstrated that the generated GRECPs allow one to carry out reliable calculations at the level of “chemical accuracy” (about 1 kcal/mol or 350 cm⁻¹ for the transition energies). A review of the calculations on lanthanide compounds with the present and earlier generated GRECPs has been given.