The effect of specific ions present during the precipitation of alumina precursor (aluminum hydroxide) on resulting alumina surface acidity has been investigated. It was found that both the method of pH control and the nature of ions introduced to the slurry apparently affected the phase composition of aluminum hydroxide as well as the strength and distribution of alumina active sites measured by means of the temperature programmed desorption of ammonia (NH3 TPD). The results were interpreted in terms of processes taking place during both polycondensation of aquo ions and aging of amorphous hydrogel of aluminum hydroxide. The ions present in the medium of precipitation (particularly at the beginning of aluminum hydroxide precipitation) apparently influenced the course of the reaction.