Jet Energy Resolution in CMS at sqrt(s)=7 TeV

We present the measurement of the CMS jet energy resolutions. Results from detailed Monte Carlo studies are compared with determinations from the collider data based on up to 35~pb$^{-1}$ of proton-proton LHC collisions at 7~TeV center of mass energy collected during the 2010 data run. Measurements of both the core and the tails of the jet energy resolutions, along with their systematic uncertainties, are presented for three different approaches to reconstruct jets in the CMS detector, using dijet and photon-jet samples.