Based on extensional viscosities measured on narrow molecular weight distributed (NMMD) polystyrenes and polystyrene oligomer dilutions thereof, we discuss the relation between the flow physics of polymer solutions and melts. A polymer solution is here characterized as a dilution where the diluent contains less than two Kuhn steps. At the same entanglement number (e.g. concentrations) its extensional viscosities are up to about 300% higher than the corresponding viscosities for polymer blends. A blend is understood as a polymer system diluted with polymer/oligomer containing active chain in term of Kuhn steps, e.g. at least two Kuhn steps. A similar disagreement is observed between blends and pure NMMD melts, both containing the same entanglement number. (C) 2013 Elsevier B.V. All rights reserved.