While some microRNAs are transcribed from a specific promoter, at least one third of human miRNA genes are clustered, wherein multiple miRNA genes are generated from a single primary transcript such as miR-17 similar to 92 cluster. Although six members of the cluster are generated from a single transcript, the mature level of each member may be diverse in various cell types. Here, we attempt to monitor the mature level of miR-17, miR-92a, and miR-20a from miR-17 similar to 92 cluster in blood (HL60 (human promyelocytic leukemia cells) and Jurkat) and breast (MDA-MB-231 and MCF-7) cancer cell lines. Interestingly, different mature levels of the miRNAs were observed in each cell line. While miR-20 was highly matured in HL60 and MDA-MB-231 cell lines, higher mature level of miR-92a was observed in Jurkat cell line compared to that of miR-20 and miR-17. Further, the mature level of miRNAs was also measured in normal and cancer cell lines. Although the mature level of miR-17 and miR-92a increased in HL60 and Jurkat cell lines, miR-20 expression showed an almost identical level in blood cancer cell lines compared to controls. Conversely, miR-20 mature level significantly increased in breast cancer cell lines whereas the expression level of miR-92a was comparable in MDA-MB-231, MCF-7, and MCF-10A cell lines.