An acidic aqueous composition for electrolytic copper plating, the composition comprising (i) copper ions, (ii) one or more than one compound of Formula (Ia) wherein - R 4 and R 5 are independently selected from the group consisting of hydrogen, methyl, ethyl, linear C3 to C16 alkyl, branched C3 to C16 alkyl and a moiety of Formula (IIa) - R 1, R 2, R 3 and R 6 are independently selected from the group consisting of hydrogen, methyl and ethyl, - B 1, B 2, B 3, D 1, D 2, and D 3 are independently selected from the group consisting of O and NH, - A 1, A 2 and A 3 independently denote a moiety selected from the group consisting of - hydrogen, methyl, ethyl, linear C3 to C16 alkyl and branched C3 to C16 alkyl, - wherein R 7 and R 8 are independently selected from the group consisting of hydrogen, methyl, ethyl, linear C3 to C10 alkyl and branched C3 to C10 alkyl, and - with the proviso that - at least one of A 1, A 2 and A 3 is a moiety selected from the group consisting of and - the corresponding B 1, B 2, and B 3 of the at least one of A 1, A 2 and A 3 is O if the corresponding x, y, and z is 1, - a, b and c are independently 0, 1, 2 or 3, - s, x, y, and z are independently 0 or 1, - n independently is 1, 2 or 3, - o + p + q + t= 5 to 300, and (iii) one, two, three or more than three further compounds, which are different from the compound of Formula (Ia), and wherein the pH value of the composition is 3 or less. (i) copper ions, (ii) one or more than one compound of Formula (Ia) wherein - R 4 and R 5 are independently selected from the group consisting of hydrogen, methyl, ethyl, linear C3 to C16 alkyl, branched C3 to C16 alkyl and a moiety of Formula (IIa) - R 1, R 2, R 3 and R 6 are independently selected from the group consisting of hydrogen, methyl and ethyl, - B 1, B 2, B 3, D 1, D 2, and D 3 are independently selected from the group consisting of O and NH, - A 1, A 2 and A 3 independently denote a moiety selected from the group consisting of - hydrogen, methyl, ethyl, linear C3 to C16 alkyl and branched C3 to C16 alkyl, - wherein R 7 and R 8 are independently selected from the group consisting of hydrogen, methyl, ethyl, linear C3 to C10 alkyl and branched C3 to C10 alkyl, and - with the proviso that - at least one of A 1, A 2 and A 3 is a moiety selected from the group consisting of and - the corresponding B 1, B 2, and B 3 of the at least one of A 1, A 2 and A 3 is O if the corresponding x, y, and z is 1, - a, b and c are independently 0, 1, 2 or 3, - s, x, y, and z are independently 0 or 1, - n independently is 1, 2 or 3, - o + p + q + t= 5 to 300, and - R 4 and R 5 are independently selected from the group consisting of hydrogen, methyl, ethyl, linear C3 to C16 alkyl, branched C3 to C16 alkyl and a moiety of Formula (IIa) - R 1, R 2, R 3 and R 6 are independently selected from the group consisting of hydrogen, methyl and ethyl, - B 1, B 2, B 3, D 1, D 2, and D 3 are independently selected from the group consisting of O and NH, - A 1, A 2 and A 3 independently denote a moiety selected from the group consisting of - hydrogen, methyl, ethyl, linear C3 to C16 alkyl and branched C3 to C16 alkyl, - wherein R 7 and R 8 are independently selected from the group consisting of hydrogen, methyl, ethyl, linear C3 to C10 alkyl and branched C3 to C10 alkyl, and - with the proviso that - at least one of A 1, A 2 and A 3 is a moiety selected from the group consisting of and - the corresponding B 1, B 2, and B 3 of the at least one of A 1, A 2 and A 3 is O if the corresponding x, y, and z is 1, - hydrogen, methyl, ethyl, linear C3 to C16 alkyl and branched C3 to C16 alkyl, - wherein R 7 and R 8 are independently selected from the group consisting of hydrogen, methyl, ethyl, linear C3 to C10 alkyl and branched C3 to C10 alkyl, and - with the proviso that - at least one of A 1, A 2 and A 3 is a moiety selected from the group consisting of and - the corresponding B 1, B 2, and B 3 of the at least one of A 1, A 2 and A 3 is O if the corresponding x, y, and z is 1, - a, b and c are independently 0, 1, 2 or 3, - s, x, y, and z are independently 0 or 1, - n independently is 1, 2 or 3, - o + p + q + t= 5 to 300, (iii) one, two, three or more than three further compounds, which are different from the compound of Formula (Ia), and