Process for carbonylation of olefins, characterized in that at least one olefin is converted by feeding H 2 and CO in the presence of a catalytic system comprising a ruthenium complex and one or more than one ligand, wherein the ligand is an organophosphorus ligand of one of the two general formulae and: where R' and R" are the same or different and are each a radical selected from the group consisting of: (C 1 -C 12)-alkyl, (C 1 -C 12)-heteroalkyl, (C 4 -C 14)-aryl, (C 4 -C 14)-aryl-(C 1 -C 12)-alkyl, (C 4 -C 14)-aryl-O-(C 1 -C 12)-alkyl, (C 3 -C 14)-heteroaryl, (C 3 -C 14)-heteroaryl-(C 1 -C 12)-alkyl, (C 3 -C 12)-cycloalkyl, (C 3 -C 12) - cycloalkyl-(C 1 -C 12)-alkyl, (C 3 -C 12)-heterocycloalkyl, (C 3 -C 12)-heterocycloalkyl-(C 1 -C 12)-alkyl, O-(C 1 -C 12)-alkyl, O-(C 1 -C 12)-heteroalkyl, O-(C 4 -C 14)-aryl, O-(C 4 -C 14)-aryl-(C 1 -C 14)-alkyl, O-(C 3 -C 14) -heteroaryl, O-(C 3 -C 14)-heteroaryl-(C 1 -C 14)-alkyl, O-(C 3 -C 12)-cycloalkyl, O-(C 3 -C 12)-cycloalkyl-(C 1 -C 12)-alkyl, O-(C 3 -C 12)-heterocycloalkyl, O-(C 3 -C 12)-heterocycloalkyl-(C 1 -C 12)-alkyl, wherein the recited alkyl, heteroalkyl, cycloalkyl, heterocycloalkyl, aryl and heteroaryl groups are optionally substituted one or more times, and R a and R b are each selected from: hydrogen, hydroxyl, (C 1 -C 12)-alkyl, (C 1 -C 12) -heteroalkyl, (C 4 -C 14)-aryl, (C 4 -C 14)-aryl-(C 1 -C 12)-alkyl, (C 4 -C 14)-aryl-O-(C 1 -C 12)-alkyl, (C 3 -C 14)-heteroaryl, (C 3 -C 14)-heteroaryl-(C 1 -C 12)-alkyl, (C 3 -C 12)-cycloalkyl, (C 3 -C 12)-cycloalkyl-(C 1 -C 12)-alkyl, (C 3 -C 12)-heterocycloalkyl, (C 3 -C 12)-heterocycloalkyl-(C 1 -C 12)-alkyl, O-(C 1 -C 12)-alkyl, O-(C 1 -C 12)-heteroalkyl, O-(C 4 -C 14)-aryl, O-(C 4 -C 14)-aryl-(C 1 -C 14)-alkyl, O-(C 3 -C 14)-heteroaryl, O-(C 3 -C 14)-heteroaryl-(C 1 -C 14)-alkyl, O-(C 3 -C 12)-cycloalkyl, 0-(C 3 -C 12)-cycloalkyl-(C 1 -C 12)-alkyl, O-(C 3 -C 12)-heterocycloalkyl, O-(C 3 -C 12)-heterocycloalkyl-(C 1 -C 12)-alkyl, wherein the recited alkyl, heteroalkyl, cycloalkyl, heterocycloalkyl, aryl and heteroaryl groups are optionally substituted one or more times, and wherein R a is also capable of forming a larger fused ring, and X is selected from: N, C. R' and R" are the same or different and are each a radical selected from the group consisting of: (C 1 -C 12)-alkyl, (C 1 -C 12)-heteroalkyl, (C 4 -C 14)-aryl, (C 4 -C 14)-aryl-(C 1 -C 12)-alkyl, (C 4 -C 14)-aryl-O-(C 1 -C 12)-alkyl, (C 3 -C 14)-heteroaryl, (C 3 -C 14)-heteroaryl-(C 1 -C 12)-alkyl, (C 3 -C 12)-cycloalkyl, (C 3 -C 12) - cycloalkyl-(C 1 -C 12)-alkyl, (C 3 -C 12)-heterocycloalkyl, (C 3 -C 12)-heterocycloalkyl-(C 1 -C 12)-alkyl, O-(C 1 -C 12)-alkyl, O-(C 1 -C 12)-heteroalkyl, O-(C 4 -C 14)-aryl, O-(C 4 -C 14)-aryl-(C 1 -C 14)-alkyl, O-(C 3 -C 14) -heteroaryl, O-(C 3 -C 14)-heteroaryl-(C 1 -C 14)-alkyl, O-(C 3 -C 12)-cycloalkyl, O-(C 3 -C 12)-cycloalkyl-(C 1 -C 12)-alkyl, O-(C 3 -C 12)-heterocycloalkyl, O-(C 3 -C 12)-heterocycloalkyl-(C 1 -C 12)-alkyl, wherein the recited alkyl, heteroalkyl, cycloalkyl, heterocycloalkyl, aryl and heteroaryl groups are optionally substituted one or more times, and (C 1 -C 12)-alkyl, (C 1 -C 12)-heteroalkyl, (C 4 -C 14)-aryl, (C 4 -C 14)-aryl-(C 1 -C 12)-alkyl, (C 4 -C 14)-aryl-O-(C 1 -C 12)-alkyl, (C 3 -C 14)-heteroaryl, (C 3 -C 14)-heteroaryl-(C 1 -C 12)-alkyl, (C 3 -C 12)-cycloalkyl, (C 3 -C 12) - cycloalkyl-(C 1 -C 12)-alkyl, (C 3 -C 12)-heterocycloalkyl, (C 3 -C 12)-heterocycloalkyl-(C 1 -C 12)-alkyl, O-(C 1 -C 12)-alkyl, O-(C 1 -C 12)-heteroalkyl, O-(C 4 -C 14)-aryl, O-(C 4 -C 14)-aryl-(C 1 -C 14)-alkyl, O-(C 3 -C 14) -heteroaryl, O-(C 3 -C 14)-heteroaryl-(C 1 -C 14)-alkyl, O-(C 3 -C 12)-cycloalkyl, O-(C 3 -C 12)-cycloalkyl-(C 1 -C 12)-alkyl, O-(C 3 -C 12)-heterocycloalkyl, O-(C 3 -C 12)-heterocycloalkyl-(C 1 -C 12)-alkyl, wherein the recited alkyl, heteroalkyl, cycloalkyl, heterocycloalkyl, aryl and heteroaryl groups are optionally substituted one or more times, and R a and R b are each selected from: hydrogen, hydroxyl, (C 1 -C 12)-alkyl, (C 1 -C 12) -heteroalkyl, (C 4 -C 14)-aryl, (C 4 -C 14)-aryl-(C 1 -C 12)-alkyl, (C 4 -C 14)-aryl-O-(C 1 -C 12)-alkyl, (C 3 -C 14)-heteroaryl, (C 3 -C 14)-heteroaryl-(C 1 -C 12)-alkyl, (C 3 -C 12)-cycloalkyl, (C 3 -C 12)-cycloalkyl-(C 1 -C 12)-alkyl, (C 3 -C 12)-heterocycloalkyl, (C 3 -C 12)-heterocycloalkyl-(C 1 -C 12)-alkyl, O-(C 1 -C 12)-alkyl, O-(C 1 -C 12)-heteroalkyl, O-(C 4 -C 14)-aryl, O-(C 4 -C 14)-aryl-(C 1 -C 14)-alkyl, O-(C 3 -C 14)-heteroaryl, O-(C 3 -C 14)-heteroaryl-(C 1 -C 14)-alkyl, O-(C 3 -C 12)-cycloalkyl, 0-(C 3 -C 12)-cycloalkyl-(C 1 -C 12)-alkyl, O-(C 3 -C 12)-heterocycloalkyl, O-(C 3 -C 12)-heterocycloalkyl-(C 1 -C 12)-alkyl,