The physicochemical properties of cobalt dispersed catalysts (10-30 wt.% of Co) on supports (SiO2, TiO2, Al2O3) for Fischer - Tropsch synthesis have been investigated. The supported metal catalysts were prepared by the wet impregnation method. Catalysts and their precursors were characterized by thermogravimetric analysis coupled with mass spectrometer (TG-DTA-MS), BET and TPR methods. It was found that specific surface area of Co3O4 supported on different supports SiO2, TiO2, Al2O3 decreased for all catalysts in function of increasing metal loading. The decomposition of catalysts precursor Co(NO3)2/support takes place according to three step process: dehydration, oxidative decomposition of cobalt(II) nitrate to Co3O4 and high temperature reductive decomposition of Co3O4 to CoO. Two-step hydrogen reduction of supported cobalt oxide phase occurs in the following sequence: Co3O4 → CoO → Co.