A process for the transformation of lignocellulosic biomass or cellulose into mono- or poly-oxygenated compounds, in which the lignocellulosic biomass or the cellulose is brought into simultaneous contact with a combination of one or more homogeneous catalysts and one or more heterogeneous catalysts in the same reaction chamber, in the presence of at least one solvent, said solvent being water alone or as a mixture with at least one other solvent, in a reducing atmosphere, and at a temperature in the range 80°C to 250°C and at a pressure in the range 0.5 MPa to 20 MPa, - said homogeneous catalyst or catalysts comprising a metallic salt which may or may not be hydrated with general formula MX n.n'H 2 O in which M is a metal selected from the metals from groups 3 to 16 of the periodic classification, n is a whole number in the range 1 to 6 and n' is a whole number in the range 0 to 6 and X is at least one anion selected from halides, nitrates, carboxylates, halocarboxylates, acetylacetonates, alcoholates, phenolates, which may or may not be substituted, sulphates, alkylsulphates, phosphates, alkylphosphates, halosulphonates, alkylsulphonates, perhaloalkylsulphonates, bis(perhaloalkylsulphonyl)amides, arenesulphonates, which may or may not be substituted with halogen or haloalkyl groups, said anions X possibly being identical or different in the case in which n is greater than 1, - said heterogeneous catalyst or catalysts comprising at least one metal selected from metals from groups 6 to 11 and metals from group 14 of the periodic classification and a support selected from oxides of elements selected from aluminium, titanium, silicon, zirconium, cerium and niobium, and mixed oxides selected from zinc, copper and cobalt aluminates, said oxides possibly being doped or not doped with at least one metallic compound selected from tungsten, tin, molybdenum and antimony, used alone or as a mixture, crystalline or non-crystalline aluminosilicates, aluminophosphates and amorphous or crystalline carbon compounds. - said homogeneous catalyst or catalysts comprising a metallic salt which may or may not be hydrated with general formula MX n.n'H 2 O in which M is a metal selected from the metals from groups 3 to 16 of the periodic classification, n is a whole number in the range 1 to 6 and n' is a whole number in the range 0 to 6 and X is at least one anion selected from halides, nitrates, carboxylates, halocarboxylates, acetylacetonates, alcoholates, phenolates, which may or may not be substituted, sulphates, alkylsulphates, phosphates, alkylphosphates, halosulphonates, alkylsulphonates, perhaloalkylsulphonates, bis(perhaloalkylsulphonyl)amides, arenesulphonates, which may or may not be substituted with halogen or haloalkyl groups, said anions X possibly being identical or different in the case in which n is greater than 1, - said heterogeneous catalyst or catalysts comprising at least one metal selected from metals from groups 6 to 11 and metals from group 14 of the periodic classification and a support selected from oxides of elements selected from aluminium, titanium, silicon, zirconium, cerium and niobium, and mixed oxides selected from zinc, copper and cobalt aluminates, said oxides possibly being doped or not doped with at least one metallic compound selected from tungsten, tin, molybdenum and antimony, used alone or as a mixture, crystalline or non-crystalline aluminosilicates, aluminophosphates and amorphous or crystalline carbon compounds.