The present invention relates to a complexed RNA, comprising at least one RNA complexed with one or more oligopeptides, wherein the oligopeptide, which has the function of cell-penetrating peptide (CPP), has a length of 8 to 15 amino acids and has the empirical formula (Arg)l;(Lys)m;(His)n;(Om)o;(Xaa)x with the majority of residues being selected from Arg, Lys, His, Om. The invention further relates to a method for transfecting a cell or an organism, thereby applying the inventive complexed RNA. Additionally, pharmaceutical compositions and kits comprising the inventive complexed RNA, as well as the use of the inventive complexed RNA for transfecting a cell, tissue or an organism and/or for modulating, preferably inducing or enhancing, an immune response are disclosed herein.