  The lecture is devoted to the comparison of a few models of cosmic
recombination kinetics with recent CMB anisotropy data and to corresponding
predictions for the upcoming PLANCK mission. The influence of additional
sources of ionized photons at the epoch of hydrogen recombination may restrict
our possibility to estimate the density of baryonic fraction of matter when
using PLANCK data. This new source of degeneracy of the cosmological parameters
which can be estimated from the CMB anisotropy data can mimic the distortion of
the CMB power spectrum for different models of baryonic matter. I would like to
point out that realistic values of the cosmological parameters can not be
obtained without PLANCK polarization data.
