Aqueous dispersions of single-walled carbon nanotubes (SWCNT) with polymers were characterized by small-angle neutron scattering (SANS) and cryo-transmission electron microscopy (cryo-TEM). Two types of polymers were used: an alternating copolymer of styrene and sodium maleate (PSSty) and gum arabic (GA)-a highly branched polysaccharide. The resulting dispersions were stable and had a homogeneous dark inklike appearance. The dispersions consisted mainly of long isolated nanotubes and thin bundles, as revealed by cryo-TEM. The scattering patterns of both dispersions were fit by a modification of Pedersen's "block copolymer micelle" model, depicting the nanotubes-polymer complex as a thick cylinder hybrid. This hybrid is made of a thin core with radius of about 20 angstrom containing similar to 4 nanotubes surrounded by a thick corona of swollen polymer coils with a radius of gyration of 150-170 angstrom. Long-term stabilization is achieved by the steric barrier provided by the adsorbed polymer coils reinforced by electrostatic repulsion due to charged groups distributed along the polymers.