The paper discusses the difference between the kinetic and hydrodynamic descriptions of nonlinear wave scattering and mixing in a plasma with an external magnetic field. Solving the kinetic equation by the method of moments makes it possible to substantiate the validity and to find the applicability range of the fluid approach to the study of nonlinear plasma processes. In the case of cold magnetoactive plasmas, the nonlinear kinetic equation and the fluid-approximation equation are shown to yield the same expression for the current that induces scattered waves. An additional effect of electromagnetic wave scattering caused by the thermal dispersion of fluctuations is considered. The current that induces scattered waves is anali zed as a function of the scattered wave frequency