The syntheses of MCM-41 (Mobil Composition of Matter No. 41) supported chromium oxide cat-alysts at different chromium concentrations (4–10 % by mass) were carried out hydrothermally. The aim of this study was to determine the effect of chromium concentration in the catalyst structure on the chro-mate types and chromium oxidation states, as well as the activity of the catalyst in the isobutane dehydro-genation reaction. Inactive α-Cr2O3 crystals for isobutane dehydrogenation were shown to increase in the catalyst structure as the chromium loading increased. The highest amount of Cr6+ on the catalyst surface was detected in the catalyst (H4-MCM-41) with 4 % chromium by mass. Catalytic tests (T = 600 °C, P = atmospheric pressure, WHSV = 26 h–1) were performed under fixed bed reactor conditions. The high-est isobutane conversion (~60 %) and selectivity (~80 %) were observed on the H4-MCM-41 catalyst, which had the highest amount of Cr6+ and monochromate structures. Catalyst deactivation was not due to coke deposition but, rather, was caused by the formation of inactive α-Cr2O3 crystal structures.