The present invention relates to oligomers, polymers and lipidoids comprising characteristic oligo(alkylene amine) moieties which are useful as vehicles for transfecting a cell with RNA. The present invention furthermore relates to a composition comprising at least a nucleic acid and an oligomer or polymer or a lipidoid comprising such oligo(alkylene amine) moieties and to a method of transfecting a cell using said composition. Furthermore, the present invention relates to pharmaceutical compositions and uses.