A double stranded iRNA agent having a first strand and a second strand, wherein at least one subunit having the structure shown in formula (I') is incorporated into at least one of said strands, wherein: A and B are each independently for each occurrence O, N(R N) or S; X is H, a protecting group, a phosphate group, a phosphodiester group, an activated phosphate group, an activated phosphite group, a phosphoramidite, a solid support, -P(Z')(Z")O-nucleoside, -P(Z')(Z")O-oligonucleotide, a lipid, a PEG, a steroid, a polymer, -P(Z')(Z")O-L 6 -Q'-L 7 -P(Z,")(Z"")O-oligonucleotide, a nucleotide, or an oligonucleotide; Y is H, a protecting group, a phosphate group, a phosphodiester group, an activated phosphate group, an activated phosphite group, a phosphoramidite, a solid support, -P(Z')(Z")O-nucleoside, -P(Z')(Z")O-oligonucleotide, a lipid, a PEG, a steroid, a lipophile, a polymer, -P(Z')(Z")O-L 6 -Q'-L 7 -OP(Z,")(Z"")O-oligonucleotide, a nucleotide, or an oligonucleotide; wherein at least one of X or Y is a -P(Z')(Z")O-nucleoside, -P(Z')(Z")O-oligonucleotide, -P(Z')(Z")O-L6-Q'-L'-P(Z"')(Z"")O-oligonucleotide, a nucleotide, or an oligonucleotide; R is chosen from a group consisting of L 6 and L 7 are each independently for each occurrence -(CH 2) n -, -C(R')(R")(CH 2)n-, -(CH 2) n C(R')(R")-, -(CH 2 CH 2 O) m CH 2 CH 2 -, or -(CH 2 CH 2 O) m CH 2 CH 2 NH-; Q' is NH, O, S, CH 2, C O, C NH, -NH-CH(R a)- -, -C -CH(R a)-NH-, CO, R a is H or amino acid side chain; R' and R" are each independently H, CH 3, OH, SH, NH 2, NH(Alkyl) or N(diAlkyl); Z', Z", Z"' and Z"" are independently O or S; n represent independently for each occurrence 1-20; and m represent independently for each occurrence 0-50, wherein the iRNA agent further comprises at least one subunit having the structure shown in formula which is incorporated into a least one of said strands, wherein X 6 and Y 6 are each independently H, 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")O-nucleoside, -P(Z')(Z")O-oligonucleotide, a lipid, a PEG, a steroid, a polymer, -P(Z')(Z")O-R 1 -Q'-R 2 -OP(Z''')(Z"")O-oligonucleotide, a nucleotide, or an oligonucleotide, -P(Z')(Z")-formula(I') or -P(Z')(Z")-; Q 6 is absent or -(P 6 -Q 7 -R 6) v -T 6 -; P 6 and T 6 are each independently for each occurrence absent, CO, NH, O, S, OC, Ni-iC, CH 2, CH 2 NH or CH 2 O; Q 7 is independently for each occurrence absent, alkylene wherein one or more methylenes can be interrupted or terminated by one or more of O, S, S, SO 2, N(R N), C(R')=C(R'), C=C or C; R 6 is independently for each occurrence absent, NH, O, S, CH 2, C O, C NH, NHCH(R a)C, -C -CH(R a)-NH-, CO, CH=N-O, or heterocyclyl; R' and R" are each independently H, C 1 -C 6 alkyl, OH, SH, N(R N) 2; R N is independently for each occurrence methyl, ethyl, propyl, isopropyl, butyl or benzyl; R a is H or amino acid side chain; Z', Z", Z'" and Z"" are each independently for each occurrence O or S; v represent independently for each occurrence 0-20; R L is a lipophile, namely cholesterol. A and B are each independently for each occurrence O, N(R N) or S; X is H, a protecting group, a phosphate group, a phosphodiester group, an activated phosphate group, an activated phosphite group, a phosphoramidite, a solid support, -P(Z')(Z")O-nucleoside, -P(Z')(Z")O-oligonucleotide, a lipid, a PEG, a steroid, a polymer, -P(Z')(Z")O-L 6 -Q'-L 7 -P(Z,")(Z"")O-oligonucleotide, a nucleotide, or an oligonucleotide; Y is H, a protecting group, a phosphate group, a phosphodiester group, an activated phosphate group, an activated phosphite group, a phosphoramidite, a solid support, -P(Z')(Z")O-nucleoside, -P(Z')(Z")O-oligonucleotide, a lipid, a PEG, a steroid, a lipophile, a polymer, -P(Z')(Z")O-L 6 -Q'-L 7 -OP(Z,")(Z"")O-oligonucleotide, a nucleotide, or an oligonucleotide; wherein at least one of X or Y is a -P(Z')(Z")O-nucleoside, -P(Z')(Z")O-oligonucleotide, -P(Z')(Z")O-L6-Q'-L'-P(Z"')(Z"")O-oligonucleotide, a nucleotide, or an oligonucleotide; R is chosen from a group consisting of L 6 and L 7 are each independently for each occurrence -(CH 2) n -, -C(R')(R")(CH 2)n-, -(CH 2) n C(R')(R")-, -(CH 2 CH 2 O) m CH 2 CH 2 -, or -(CH 2 CH 2 O) m CH 2 CH 2 NH-; Q' is NH, O, S, CH 2, C O, C NH, -NH-CH(R a)- -, -C -CH(R a)-NH-, CO, R a is H or amino acid side chain; R' and R" are each independently H, CH 3, OH, SH, NH 2, NH(Alkyl) or N(diAlkyl); Z', Z", Z"' and Z"" are independently O or S; n represent independently for each occurrence 1-20; and m represent independently for each occurrence 0-50,