Ficoll PM70 is an important branched polysaccharide polymer with a variety of applications in biology and biophysics. The accepted picture for the aqueous solutions of this polymer is that of a polydisperse nearly spherical suspension with a molecular weight of 70.0 kDa and a hydrodynamic radius alpha = (4.70 +/- 0.04) nm. This was confirmed by dynamic and static light scattering on a wide range of concentrations and at three different temperatures. Further, dynamic light scattering experiments indicated the coexistence of two closely-spaced diffusive modes in solution by analyzing the spectra with double exponential fits. The impact of these, concentration dependent, diffusive modes in Ficoll PM70 solutions is discussed in the context of multicomponent molecular crowding studies. (c) 2012 Elsevier Inc. All rights reserved.