  We calculated the cross section for the exclusive double diffractive $b\bar
b$ production in $pp\to p(b\bar b)p$ reaction at LHC. Large cross sections are
obtained (3 -- 10 nb). This process constitutes the irreducible background to
the exclusive Higgs production and is of particular importance in the upcoming
Higgs boson searches. The distribution in invariant mass of the $b \bar b$ pair
is calculated and compared with the corresponding contribution from the Higgs
decay. The contribution from the exclusive production of $Z^0$ and its decay as
well as the contribution from the $\gamma \gamma \to b \bar b$ subprocess are
also presented for the first time. The influence of cuts on the
signal-to-background ratio is discussed.
