Aluminium hydroxides were precipitated from sodium aluminate using ammonium salt solutions. The effect of the kind of ammonium salt used for the aluminium hydroxide precipitation on the surface properties of the related alumina was investigated. It was stated that kind of ammonium salt affects the aluminium hydroxide phase composition as well as the Lewis acid site surface concentration and the concentration of anionic OH- groups; the specific acidity was measured by means of TPD NH3 and the specific rate of cyclohexene isomerization. DRS spectra of the Mo catalyst supported on investigated aluminas as well as the RDS activity vary with the kind of ammonium salt. The obtained results are explained on the basis of processes both during polycondensation of aquo-ions Al-III and during ageing of amorphous hydrogel of aluminium hydroxide. Results are discussed on the basis of the literature.