PURPOSE: The aim of this study is to search for new therapeutic targets for atypical teratoid-rhabdoid tumors (ATRT). METHODS: To achieve this, we compared the expression of 365 microRNAs among ATRT, medulloblastomas, and normal brain. RESULTS: MiR-221 and miR-222 were within the top differentially expressed microRNAs. The deregulated expression of miR221/222 was demonstrated to inhibit the expression of the tumor suppressor and inhibitor of cell cycle p27(Kip1). Here, we demonstrated the negative regulation of p27(Kip1) by miR-221/222 in ATRT using microarray, real-time reverse transcriptase polymerase chain reaction, and immunohistochemistry. CONCLUSION: As anti-miR therapy was recently proposed as an alternative treatment for cancer, these findings suggest that anti-miR-221/222 therapy might have therapeutic potential in ATRT.