Fibrous ion exchangers appear to be very promising for full scale applications in water conditioning (demineralization, softening), wastewater treatment for pollutant control, as well as for applications in new areas promoted by the physical structure of the materials. The kinetic performances of these exchangers appear to be faster than traditional bead-shaped resins. In a previous paper, the kinetic behavior of chloride/sulfate ion exchange system on fibrous resins was investigated in a wide range of liquid-phase concentrations (i.e., 0.006-1.8 N). The Nernst-Planck model was adopted for data correlation, and the rate-determining step was associated with the mass transfer resistance to the interdiffusion of ions in the liquid film around the microfibers. In the present paper, the same data are revisited on the basis of an alternative model for film diffusion control, based on the numerical solution of a phenomenological equation accounting for the selectivity of the resin toward the exchanging counterions. In this context, equilibrium studies were also carried out and criticized to get relevant data for model implementation. Both kinetic models gave equivalent results in experimental data correlation, thus confirming the exposed surface area of the fibrous exchangers, a more important factor with respect to selectivity in determining the peculiar kinetic performance of these materials.