The tendency for hard and irregular particles of titanium dioxide pigment to adversely affect the sheen and coin mar resistance of a dried coating into which they have been incorporated is reduced by modifying the particles with polymer particles which have been preformed and are therefore of a more pre-determinable shape and size. The polymer particles are chemically bonded to a polymeric water-soluble compound containing moieties which are adsorbable onto the titanium dioxide particles so that on mixing a colloidally stabilised aqueous dispersion of the polymer particles with a colloidally stabilised aqueous dispersion of titanium dioxide particles, the moieties adsorb onto the titanium dioxide to form a colloidally stable aqueous dispersion of polymer-modified titanium dioxide which is useful in coating compositions.