The poly(ethylene oxide) (PEO) induced flocculation of polystyrene latex (PS) and polystyrene-core poly(p-vinylphenol)-shell (PS-PVPh) latexes were compared. PEO gave much more effective flocculation of the core-shell particles, and flocculation was observed over a much greater range of PEO concentrations. The core-shell particles were able to adsorb 6-7 times more PEO than comparable sized polystyrene latex. It is proposed that the efficient flocculation and the PEO high adsorption capacity of core-shell particles shows that adsorbed PEO molecules do not spread upon the poly(vinylphenol) surface. The polymer spreading model of Pelssers, Cohen Stuart, and Fleer was extended to account for the available surface area when an adsorbed flocculant, molecule spreads on a surface. The revised model, coupled with conventional kinetic expressions for flocculation and polymer adsorption, gave good predictions of a wide variety of flocculation behaviors.