The problem of resonant ion tail formation during ICRF heating of tokamak plasmas is considered. Using the fact that the RF diffusion and Fast-ion Fokker-Planck equations admit simple solution procedures, a method is given for the determination of the solution of the time dependent ICRF Fokker-Planck equation in the small Larmor-radius approximation (r.k,<<1). The solution procedure leads to a Volterra integral equation for the determination of the effect of the Coulomb scattering processes on tail formation. Then using an iterative-perturbation technique, the problem of tail formation during heating at the fundamental (n = 1) and second harmonic (n = 2) frequencies is addressed.