Both low molecular weight and high molecular weight aromatic and heteroaromatic compounds which are substituted by olefins play an important role in industry, for instance as assistants and additives in cosmetic preparations, for example in sunscreens, various fine and electronics chemicals, and precursors for pharmaceuticals and agrochemicals. Also, particularly in the rapidly growing field of organic semiconductors (for example applications in organic or polymeric light emitting diodes, organic solar cells, organic ICs), precisely these compounds are of outstanding significance.The present invention relates to a process for preparing such olefin-substituted aromatics or heteroaromatics by reacting a functional aryl or heteroaryl compound with an olefin derivative which has at least one hydrogen atom on the double bond in the presence of a simple palladium compound, optionally in the presence of a nitrogen additive, and of a base in a solvent, to form a C--C bond and formally cleave off the functional group of the aryl or heteroaryl derivative and a hydrogen atom of the olefin compound, characterized by the presence of at least one metal additive other than palladium.