This invention provides compounds, compositions and methods for modulating the expression of human GST-pi using RNA interference. The RNA interference molecules can be used in methods for preventing or treating diseases such as malignant tumor. Provided are a range of siRNA structures, having one or more of nucleotides being modified or chemically-modified. Advantageous structures include siRNAs with 2-deoxy nucleotides located in the seed region, as well as other nucleotide modifications