We examined expression profiles of hematopoietic tissue-specific microRNAs (miRNAs; miR-142, miR-155, miR-181 and miR-223) in 17 commercially available malignant hematopoietic cell lines and compared to those in highly purified normal human B, T, monocytic and granulocytic lineages. Although malignant cell lines examined showed miRNA expression patterns similar to normal human hematopoietic lineages, the levels of miRNA expression among cell lines and normal cell lineages were considerably different, indicating the significance of miRNAs in human hematopoietic diseases. Further our results showed differences in miRNA expression between mouse and human hematopoietic cells, suggesting important regulatory roles of miRNAs in human hematopoiesis and oncogenesis.