The Jefferson Lab Angular Momentum (JAM) collaboration is a new initiative aimed at the study of the angular-momentum-dependent structure of the nucleon. First results on the determination of spin-dependent parton distribution functions from world data on polarized deep-inelastic Scattering will be presented. In the second part of the talk the ongoing update of the JR unpolarized parton distributions will be reported. Different aspects or polarized and unpolarized global QCD analysis will be discussed, including effects due to the nuclear structure of targets, target-mass corrections and higher twist contributions to the structure functions