Process for producing polyurethane foam by reacting at least one polyol component with at least one isocyanate component in the presence of at least one blowing agent and of one or more catalysts that catalyse the isocyanate-polyol and/or isocyanate-water reactions and/or isocyanate trimerization, characterized in that the reaction is conducted in the presence of polyethersiloxane copolymer of the formula M a D b D' c with R 1 = independently identical or different hydrocarbyl radicals having 1 to 16 carbon atoms or H, preferably methyl, ethyl, propyl and phenyl, especially preferably methyl, R 2 = independently R 1 or R 3, R 3 = independently identical or different polyether radicals, preferably polyether radicals of the general formula -R 4 O[C 2 H 4 O] d [C 3 H 6 O] e R 5, R 4 = identical or different divalent hydrocarbyl radicals which have 1 to 16 carbon atoms and may optionally be interrupted by oxygen atoms, preferably a radical of the general formula with f = 1 to 8, preferably 3, R 5 = independently identical or different hydrocarbyl radicals which have 1 to 16 carbon atoms and may optionally be interrupted by urethane functions, -C NH-, carbonyl functions or -C O-, or H, preferably methyl, -C Me or H, with a = 2, a + b + c = 10 to 200, preferably 20 to 80, especially preferably 20 to 50, b/c = 15 to 50, d and e = numerical averages which arise from the following provisos: with the provisos that the molar mass (numerical average M n) of the individual polyether radicals R 3 = 600 to 2000 g/mol, preferably 700 to 1800 g/mol, especially preferably 800 to 1700 g/mol, that at least one R 3 radical present has a molar mass formed to an extent of 27% to 60% by mass, preferably to an extent of 30% to 50% by mass and especially preferably to an extent of 35% to 45% by mass from -[C 3 H 6 O]- units, that the percentage siloxane content in the polyethersiloxane copolymer is 35% to 60% by mass, preferably 40% to 60% by mass, especially preferably 45% to 55% by mass, and wherein the polyether siloxanes of the formula I are used in a total proportion by mass of 0.1 to 10 parts, preferably of 0.5 to 5 parts, especially preferably of 1 to 3 parts, based on 100 parts by mass of polyol component. R 1 = independently identical or different hydrocarbyl radicals having 1 to 16 carbon atoms or H, preferably methyl, ethyl, propyl and phenyl, especially preferably methyl, R 2 = independently R 1 or R 3, R 3 = independently identical or different polyether radicals, preferably polyether radicals of the general formula -R 4 O[C 2 H 4 O] d [C 3 H 6 O] e R 5, R 4 = identical or different divalent hydrocarbyl radicals which have 1 to 16 carbon atoms and may optionally be interrupted by oxygen atoms, preferably a radical of the general formula with f = 1 to 8, preferably 3, R 5 = independently identical or different hydrocarbyl radicals which have 1 to 16 carbon atoms and may optionally be interrupted by urethane functions, -C NH-, carbonyl functions or -C O-, or H, preferably methyl, -C Me or H, with a = 2, a + b + c = 10 to 200, preferably 20 to 80, especially preferably 20 to 50, b/c = 15 to 50, d and e = numerical averages which arise from the following provisos: with the provisos that the molar mass (numerical average M n) of the individual polyether radicals R 3 = 600 to 2000 g/mol, preferably 700 to 1800 g/mol, especially preferably 800 to 1700 g/mol, that at least one R 3 radical present has a molar mass formed to an extent of 27% to 60% by mass, preferably to an extent of 30% to 50% by mass and especially preferably to an extent of 35% to 45% by mass from -[C 3 H 6 O]- units, that the percentage siloxane content in the polyethersiloxane copolymer is 35% to 60% by mass, preferably 40% to 60% by mass, especially preferably 45% to 55% by mass, and wherein the polyether siloxanes of the formula I are used in a total proportion by mass of 0.1 to 10 parts, preferably of 0.5 to 5 parts, especially preferably of 1 to 3 parts, based on 100 parts by mass of polyol component. with the provisos that the molar mass (numerical average M n) of the individual polyether radicals R 3 = 600 to 2000 g/mol, preferably 700 to 1800 g/mol, especially preferably 800 to 1700 g/mol, that at least one R 3 radical present has a molar mass formed to an extent of 27% to 60% by mass, preferably to an extent of 30% to 50% by mass and especially preferably to an extent of 35% to 45% by mass from -[C 3 H 6 O]- units, that the percentage siloxane content in the polyethersiloxane copolymer is 35% to 60% by mass, preferably 40% to 60% by mass, especially preferably 45% to 55% by mass, and wherein the polyether siloxanes of the formula I are used in a total proportion by mass of 0.1 to 10 parts, preferably of 0.5 to 5 parts, especially preferably of 1 to 3 parts, based on 100 parts by mass of polyol component.