Relativistic effects can be incorporated by fully relativistic and scalar relativistic pseudopotentials. In the fully relativistic treatment, the spin-orbit coupling is included in addition to kinematic relativistic effects (Darwin and mass velocity terms). On the other hand, the spin-orbit coupling is averaged in the scalar relativistic treatment. Although the scalar relativistic treatment can be incorporated in both the collinear and non-collinear DFT calculations, the fully relativistic treatment is supported for only the non-collinear DFT in the current version of OpenMX.