Herein, we have evaluated the effect on growth and survival by two HDAC inhibitors PCI-24781 and CI-994 in three human neuroblastoma cell lines SK-N-DZ, SH-SY-5Y and SK-N-SH, and further investigated the detailed mechanisms of PCI-24781 in SK-N-DZ cell line. The gene discussed is HDAC9; the disease is neuroblastoma.