The radius of gyration (R g ) was determined as a function of generation number for arborescent polystyrenes with two different side chain mass average molecular mass (M w ≈ 5000, 5K, versus 30 000, 30K) by small-angle neutron scattering (SANS) measurements. The R g values obtained were analyzed in terms of the Zimm-Stockmayer model for randomly branched polymers, the scaling relation R g ∝ M w V , and the expansion factor R s ) (R g ) goodsolvent /(R g ) Θsolvent . The R g and scaling exponent V ) 0.26 ( 0.01 found for G0 through G3 polymers with 5K side chains in cyclohexane-d correspond to the values predicted by the Zimm-Stockmayer model. The R g for G0 through G3 polymers with 30K side chains deviate from the model with V ) 0.32 ( 0.02, corresponding to V ) 0.33 expected for hard spheres. Deuterated polystyrene (PS-d) side chains were grafted onto G2 and G3 polystyrene (PS) cores. These copolymers, G2PS-graft-PS-d and G3PS-graft-PS-d, were characterized as spheres with a well-defined PS core-PS-d shell structure by the SANS contrast matching method. The shape and the segment radial density profile of the core and shell for GPS-graft-PS-d were determined based on P(r) and ∆F(r) obtained by indirect Fourier transformation and deconvolution methods (P(r), pair distance distribution function and ∆F(r) ) F(r) -F(solvent), scattering length density contrast profile).