The present invention is directed to novel double-stranded short interfering (siRNA) analogues comprising locked nucleic acid (LNA) monomers. Such compounds induces sequence-specific post-transcriptional gene silencing in many organisms by a process known as RNA interference (RNAi). The compounds disclosed herein has improved properties compared to non-modified siRNAs and may, accordingly, be useful as therapeutic agents, e.g., in the treatment of various cancer forms. More particularly, the present invention is directed to siRNA analogues comprising a sense strand and an antisense strand, wherein each strand comprises 12-35 nucleotides and wherein the siRNA analogues comprise at least one locked nucleic acid (LNA) monomer.