The present invention relates to a double-stranded ribonucleic acid (dsRNA) having improved efficiency of inhibition of gene expression, methods of making the dsRNA, and pharmaceutical compositions comprising the dsRNA. The dsRNA comprises an RNA strand (complementary RNA strand) having a region which is complementary to an RNA transcript of at least a part of a target gene, and at least one covalently linked lipophilic group. The dsRNA are useful for inhibiting the expression of a target gene, as well as for treating diseases caused by expression of the target gene. The invention also relates to methods for inhibiting the expression of a target gene, as well as methods for treating diseases caused by the expression of the gene.