Jet production and αs measurement at CMS

The measurements of inclusive jet, dijet and trijet cross sections, of the dijet azimuthal decorrelations, the ratio of the inclusive 3-jet to 2-jet cross sections are presented. The measurements use the samples of proton-proton collisions collected with the CMS detector at the LHC at a center-of-mass energy of 7 and 8 TeV.