VIS-NIR diffuse reflectance spectra of Co2+NaK-and Co2+H-ferrierites with Co loadings varying from 0.12 to 3.62 wt.% were studied. Three different coordinations of the Co2+ ions in Co-ferrierites dehydrated at 770 K were reflected in optical spectra, and their population depending on the Co ion concentration in both CoNaK-and CoHferrierites was determined. Site B is formed by four oxygens in a rectangle on the wall of the main ferrierite channel. The Co ions at this site, a type, are characterized by a band at 15 000 cm-1. With increasing Co concentration the population of the Co2+ ions in site B increases for CoH-ferrierite and significantly decreases for CoNaK-ferrierite.The Co2+ ion of the type b, located in site G of the ferrierite cavity, is characterized by absorption bands at 16 000, 17 100, 18 700 and 20 600 cm-1. The Co2+ ion is coordinated to framework oxygens of the deformed six-membered ring. These Co2+ ions predominate in both CoH-and CoNaK-ferrierites. Two bands at 20 300 and 22 000 cm-1 represent c-type Co2+ ions in a 'boat shaped' site C of the ferrierite cavity. The number of coordinated framework oxygens and detailed geometry of this site is not known. The Co2+ ions in this site represent a minority of Co2+ ions located in ferrierite.