The effective masses of the conductivity electrons were explored within the framework of simplified band model and for cadmium arsenide without the center of symmetry. It appeared that effective masses are distinguished in different spin sub-bands. The energy dependences of the effective masses are nonlinear with the clearly expressed minimum close to the bottom of the band. Anisotropy of the effective masses as the stronger as the less is the energy of carriers. These features are explained by the influencing of the narrow band of heavy electrons, almost degenerated with the bottom of the conductivity band.