Interfering RNA molecules

A ribonucleic acid comprising a double stranded structure whereby the double-stranded structure comprises a first strand and a second strand, whereby the first strand comprises a first stretch of contiguous nucleotides and whereby said first stretch is at least partially complementary to a target nucleic acid, and the second strand comprises a second stretch of contiguous nucleotides and whereby said second stretch is at least partially identical to a target nucleic acid, whereby the double stranded structure is blunt ended or has an overhang and contains a group of ribonucleic acids on the first or second stretch/strand that has a modification at the 2′-position selected from an amino, fluoro, methoxy, alkoxy or alkyl modification and said group of modified ribonucleic acids on the first or second stretch/strand is flanked on one or both sides by a group of flanking ribonucleic acids having a modification at the 2′-position selected from an amino, fluoro, methoxy, alkoxy or alkyl modification that is different from the modification on said group of ribonucleic acids modified at the 2′-position and the number of ribonucleic acids in the group of modified ribonucleic acids is selected from one to ten ribonucleic acids and the number of ribonucleic acids in the group of flanking ribonucleic acids is selected from one to ten ribonucleic acids.