Dihadron correlations in pp and PbPb collisions

Measurements of charged dihadron angular correlations are presented in proton-proton (pp) and Lead-Lead (PbPb) collisions, over a broad range of pseudorapidity and azimuthal angle, using the CMS detector at the LHC. A new and striking ``ridge''-like structure emerges in the two-dimensional correlation function for particle pairs with intermediate $p_{T}$ of 1-3 GeV/$c$, in the kinematic region that absolute value of eta is from 2.0 to 4.8 and small $\Delta\phi$ in very high multiplicity pp collisions at $\sqrt{s}$ = 7 TeV. Studies of the long-range and short-range dihadron correlations in PbPb collisions at $\sqrt{s_{NN}}$ = 2.76 TeV are presented as well.