  We present searches for massive top and bottom quark partners at CMS using
LHC pp collision data collected at centre-of-mass energy $\sqrt{s} = 8$ TeV.
Such partners can be found in models predicting vector-like quarks to solve the
hierarchy problem and stabilize the Higgs boson mass. The searches span a range
of final states containing several lepton and jet multiplicities, and limits
were set on mass and production cross sections as a function of branching
ratios.
