  We investigate the charged Higgs boson contribution into $t\bar b$-pair
production in pp-collisions at LHC. It is shown that due to the $\cz$-boson
exchange the total yield of $t\bar b$ is modified significantly for small and
large values of $\tan\beta$. However, for the small values of $\tan\beta$ one
should expect also the production of right-polarized top quark contrary to pure
left-polarized t-quark production through $W^{\pm}$-boson exchange only. This
fact provides a possibility to separate $H^{\pm}$ and $W^{\pm}$ contributions
by means of the investigations of angular distributions of top decay products.
The detailed simulation of the signal and relevant background processes is
performed.
