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. In very high multiplicity pp events at center-of-mass energy of 7 TeV, a striking ‘ridge’-like structure emerges in the two-dimensional correlation function for particle pairs with intermediate pT of 1–3 GeV/c, in the kinematic region 2.0 < |Δη| < 4.8 and small Δϕ, which is similar to observations in heavy-ion collisions. Studies of this new effect as a function of particle transverse momentum are discussed. The long-range and short-range dihadron correlations are also studied in PbPb collision at a nucleon–nucleon center-of-mass energy of 2.76 TeV, as a function of transverse momentum and collision centrality. A Fourier analysis of the long-range dihadron correlations is presented and discussed in the context of CMS measurements of higher order flow coefficients.