Spintronic devices require channels to efficiently conduct spin current. Carbon nanofibers based on polyacrylonitrile (PAN) are already of keen interest in nanotechnology and energy science; could they be useful in spintronics as well? Modeling PAN nanofibers as N-terminated zigzag graphene nanoribbons, the authors study the electronic structures and quantum transport properties of these quasi-one-dimensional systems as a function of width. They demonstrate that narrow ribbons bear finite magnetic moments, with spin-polarized electronic states exhibiting similar spin configurations on both edges, resulting in spin-dependent transport channels.