The present invention provides iRNA agents comprising at least one subunit of the formula (I): wherein: A and B are each independently for each occurrence O, N(R N ) or S； X and Y are each independently for each occurrence H, OH, a hydroxyl protecting group, a phosphate group, a phosphodiester group, an activated phosphate group, an activated phosphite group, a phosphoramidite, a solid support, - P(Z')(Z")0- nucleoside, -P(Z')(Z")O-oligonucleotide, a lipid, a PEG, a steroid, a lipophile, a polymer, P(Z')(Z")O-Linker-OP(Z"')(Z")O-oligonucleotide, a nucleotide, an oligonucleotide, - P(Z')(Z")-formula(I), -P(Z')(Z")- or -Linker-R； R is L G , -Linker-L G , or has the structure shown below: L G is independently for each occurence a carbohydrate, e.g., monosaccharide, disaccharide, trisaccharide, tetrasaccharide, oligosaccharide, polysaccharide； R N is independently for each occurrence H, methyl, ethyl, propyl, isopropyl, butyl, or benzyl； and Z', Z", Z'" and Z" are each independently for each occurrence O or S.
