Catalytic ketonization of aliphatic aldehydes, alcohols, acids and esters on chromium-zinc-manganese oxide catalysts with zinc chromite spinel structure has been studied previously. Brief characterization of the optimum reaction conditions and evaluation of the forming conditions of reaction by-products are given in the introduction of the paper. It has been established that the highest selectivity is shown by ketonization of aliphatic acids (96.8% acetone from acetic acid and 92.3% dipropyl ketone from butyric acid at 325 oC temperature). In the present work, catalytic cross-ketonization of aliphatic acids over zinc chromite type catalysts at the temperature range 330-400 oC in the presence of water vapour is studied; the catalysts are prepared by a new, fast and environmentally friendly method, mixing aqueous solution of CrO3 with ZnO-water suspension. The optimum ratio of zinc and chromium (1.2 – 1.5 : 1) is established. Aqueous solutions of acetic acid-propionic acid and of acetic acid-valeric acid are used as starting materials. The zinc chromite type catalysts are found to be effective in cross-ketonization reactions, as well. It is shown that, at lower temperatures, mainly the lightest ketone (acetone in our case) forms as a result of ketonization. The amount of acetone rises also with increasing acetic acid concentration in the starting mixtures. It is observed that the maximum yields of the heaviest ketones (diethyl ketone in the case of propionic acid, and dibutyl ketone in the case of valeric acid) are reached at 355 – 380 oC temperature range, diminishing with increasing acetic acid concentration in the mixtures. The maximum selectivity of unsymmetrical ketones (methyl ethyl ketone – in the case of propionic acid, and methyl butyl ketone – in the case of valeric acid) is usually higher than that of symmetric ketones; it appears at the temperature of 355 – 380 oC and slightly rises with increasing acetic acid concentration in the reactant mixtures. Under similar reaction conditions at the temperature of 330 oC, the yield of acetone is higher in the case of acetic acid-propionic acid ketonization, compared to ketonization of acetic acid-valeric acid, and the same yield is lower at 380-400 oC. In the latter case, the yield of unsymmetrical ketone is also lower. Conversion of acetic acid at all temperatures is higher than conversion of propionic acid and valeric acid.