Nuclear parton distribution functions are essential to the understanding of proton-lead collisions. We will review several measurements from CMS that are particularly sensitive to nPDFs. W and Z bosons are medium-blind probes of the initial state of the collisions, and we will present the measurements of their production cross sections in pPb collisions at 5.02 TeV, and as well a asymmetries with an increased sensitivity to nPDFs. We will also report measurements of charmonium production, including the nuclear modification factor of J/psi and psi(2S) in pPb collisions at 5.02 TeV, though other cold nuclear matter effects may also be at play in those processes. At last, we will present measurements of the pseudo-rapidity of dijets in pPb collisions at 5.02 TeV.