Skobeltsyn Institute of Nuclear Physics
Lomonosov Moscow State University

In this article we study the registration possibility of rare muonic B-mesons decays B_(d,s)^ 0 -> mu+mu- at the ATLAS decector (LHC, CERN). There is shown, which results can we obtained after three years of LHC operation at initial luminocity. We give the list of the most important non-combinatorial background processes for the rare muonic B-meson decays.