A composition, which comprises a) an organic material susceptible to oxidative, thermal or light-induced degradation, wherein the organic material is a polymer, which is a polyolefin or a copolymer thereof, a polystyrene or a copolymer thereof, or a polyurethane or a copolymer thereof, with the proviso that the polymer is not a polypeptide, agar-agar or a component of agar-agar; and b) a compound of formula I wherein n is 1, R 5 is H, C 1 -C 30 -alkyl, C 3 -C 10 -cycloalkyl, C 6 -C 10 -aryl, which is unsubstituted or substituted by C 1 -C 8 -alkyl or C 1 -C 8 -alkoxy, C 7 -C 13 -aralkyl, C 2 -C 22 -alkenyl, OH, C 1 -C 30 -alkyloxy, C 3 -C 10 -cycloalkyloxy, C 6 -C 12 -aryloxy, C 7 -C 13 -aralkyloxy, hydroxy-C 1 -C 8 -alkyl, carboxy-C 1 -C 12 -alkyl, C 1 -C 12 -alkoxycarbonyl-C 1 -C 12 -alkyl, C 2 -C 30 -alkyl, which is interrupted by one or more oxygen atoms, or NR' 1 R' 2; 3 substituents out of R 1 to R 4 and 2 substituents out of R 6 to R 9 are H and the other remaining 3 substituents out of R 1 to R 4 and R 6 to R 9 are each independently from each other H, C 1 -C 12 -alkyl, C 1 -C 12 -alkoxy or halogen; and R' 1 and R' 2 are each independently from each other H, C 1 -C 12 -alkyl, C 3 -C 10 -cycloalkyl, C 3 -C 22 -alkenyl, C 6 -C 10 -aryl, which is unsubstituted or substituted by C 1 -C 8 -alkyl or C 1 -C 8 -alkoxy, C 7 -C 12 -aralkyl, or R' 1 and R' 2 form together with the nitrogen atom, to which they are attached, a pyrrolidine, a piperidine or a morpholine ring. a) an organic material susceptible to oxidative, thermal or light-induced degradation, wherein the organic material is a polymer, which is a polyolefin or a copolymer thereof, a polystyrene or a copolymer thereof, or a polyurethane or a copolymer thereof, with the proviso that the polymer is not a polypeptide, agar-agar or a component of agar-agar; and b) a compound of formula I wherein n is 1, R 5 is H, C 1 -C 30 -alkyl, C 3 -C 10 -cycloalkyl, C 6 -C 10 -aryl, which is unsubstituted or substituted by C 1 -C 8 -alkyl or C 1 -C 8 -alkoxy, C 7 -C 13 -aralkyl, C 2 -C 22 -alkenyl, OH, C 1 -C 30 -alkyloxy, C 3 -C 10 -cycloalkyloxy, C 6 -C 12 -aryloxy, C 7 -C 13 -aralkyloxy, hydroxy-C 1 -C 8 -alkyl, carboxy-C 1 -C 12 -alkyl, C 1 -C 12 -alkoxycarbonyl-C 1 -C 12 -alkyl, C 2 -C 30 -alkyl, which is interrupted by one or more oxygen atoms, or NR' 1 R' 2; 3 substituents out of R 1 to R 4 and 2 substituents out of R 6 to R 9 are H and the other remaining 3 substituents out of R 1 to R 4 and R 6 to R 9 are each independently from each other H, C 1 -C 12 -alkyl, C 1 -C 12 -alkoxy or halogen; and R' 1 and R' 2 are each independently from each other H, C 1 -C 12 -alkyl, C 3 -C 10 -cycloalkyl, C 3 -C 22 -alkenyl, C 6 -C 10 -aryl, which is unsubstituted or substituted by C 1 -C 8 -alkyl or C 1 -C 8 -alkoxy, C 7 -C 12 -aralkyl, or R' 1 and R' 2 form together with the nitrogen atom, to which they are attached, a pyrrolidine, a piperidine or a morpholine ring. n is 1, R 5 is H, C 1 -C 30 -alkyl, C 3 -C 10 -cycloalkyl, C 6 -C 10 -aryl, which is unsubstituted or substituted by C 1 -C 8 -alkyl or C 1 -C 8 -alkoxy, C 7 -C 13 -aralkyl, C 2 -C 22 -alkenyl, OH, C 1 -C 30 -alkyloxy, C 3 -C 10 -cycloalkyloxy, C 6 -C 12 -aryloxy, C 7 -C 13 -aralkyloxy, hydroxy-C 1 -C 8 -alkyl, carboxy-C 1 -C 12 -alkyl, C 1 -C 12 -alkoxycarbonyl-C 1 -C 12 -alkyl, C 2 -C 30 -alkyl, which is interrupted by one or more oxygen atoms, or NR' 1 R' 2; 3 substituents out of R 1 to R 4 and 2 substituents out of R 6 to R 9 are H and the other remaining 3 substituents out of R 1 to R 4 and R 6 to R 9 are each independently from each other H, C 1 -C 12 -alkyl, C 1 -C 12 -alkoxy or halogen; and R' 1 and R' 2 are each independently from each other H, C 1 -C 12 -alkyl, C 3 -C 10 -cycloalkyl, C 3 -C 22 -alkenyl, C 6 -C 10 -aryl, which is unsubstituted or substituted by C 1 -C 8 -alkyl or C 1 -C 8 -alkoxy, C 7 -C 12 -aralkyl, or R' 1 and R' 2 form together with the nitrogen atom, to which they are attached, a pyrrolidine, a piperidine or a morpholine ring.