The method for the synthesis of either unmodified magnesium hydroxide or functionalised with poly(ethylene glycols) of different molecular weights and physicochemical properties of the products are presented. Magnesium hydroxide was obtained by the precipitation method under well defined conditions from ammonia solution and different magnesium salts. Dispersive properties of the products were characterised by polydispersity index, particle size, as well as SEM images. Crystalline structure of magnesium hydroxide samples were determined by the WAXS method. To confirm the presence of functional groups introduced by appropriate modifiers the samples were subjected to spectroscopic analysis. Electrokinetic stability of the studied samples was determined on the basis of zeta potential dependence vs. pH measurements. The modification has resulted in reduction of particle diameters in some Mg(OH)₂ samples.