  We systematically study the possible signals at LHC of new vector-like quarks
mainly coupled to the third generation. We consider heavy quarks T, B, X, Y of
charges 2/3, -1/3, 5/3 and -4/3, respectively, in SU(2)_L isosinglets T_{L,R},
B_{L,R}, or isodoublets (T B)_{L,R}, (X T)_{L,R} or (B Y)_{L,R}. Analyses based
on a fast detector simulation are presented for twelve different final states
containing one, two, three or four charged leptons in several invariant mass
regions, also considering various b quark multiplicities. It is shown that with
the combination of the different channels the new quarks can be identified and
their charged and neutral decays established. The comparison among final states
also shows that the single lepton one offers the best discovery potential at
LHC. For heavy quark masses of 500 GeV, the 5 sigma discovery luminosities
range from 0.16 fb^-1 for a (X T)_{L,R} doublet to 1.9 fb^-1 for a B_{L,R}
singlet.
