Concentration gradients of the chemical species in a gas mixture are known to cause movement of aerosol particles, the particle motion commonly termed 'diffusiophoresis' and the force producing this motion 'diffusion force' (Brock, 1963). This phenomenon cannot be described within the ordinary continuum theory, thus different approaches to the problem have been made until they led to the use of model gas-kinetic equations. It was F.J. McCormack (1973) who proposed a simple method of construction of linearized kinetic models for gaseous mixtures. Thus, the present paper presents an elaboration of a consistent gas-kinetic theory for the diffusion force, drag force, diffusiophoretic velocity and the study of their dependencies on the properties of aerosol particles and surrounding gas mixtures.