Résumé : Measurements are reported of the WZ and ZZ production cross sections in proton-proton collisions at s = 8 TeV in final states where one Z boson decays to b-tagged jets. The other gauge boson, either W or Z, is detected through its leptonic decay (either W → eν, μν or Z → e + e − , μ + μ − , or νν). The results are based on data corresponding to an integrated luminosity of 18.9 fb − 1 collected with the CMS detector at the Large Hadron Collider. The measured cross sections, σ ( pp → WZ ) = 30.7 ± 9.3 (stat) ± 7.1 (syst) ± 4.1 (theo) ± 1.0 (lumi) pb and σ ( pp → ZZ ) = 6.5 ± 1.7 (stat) ± 1.0 (syst) ± 0.9 (theo) ± 0.2 (lumi) pb, are consistent with next-to-leading order quantum chromodynamics calculations.