Defective dendritic cell (DC) functions have been implicated in ITP. The purpose of this study was to investigate the distribution and activation of dendritic cells in immune thrombocytopenia (ITP) patients. ITP patients were divided into 3 groups: the newly diagnosed, refractory and effective treatment group. The distributions of plasmacytoid dendritic cells (pDC) and myeloid dendritic cells (mDC) in peripheral blood, bone marrow and spleen were detected with flow cytometry. The expression level of CD80 and CD86 on surface of pDC and mDC was also detected with flow cytometry. The results indicated that the percentage of mDC was higher than that of pDC in all sites of all groups. The percentage of mDC and pDC in all site of refractory group was higher than that in newly diagnosed and effective groups, but the percentage of mDC in spleen of refractory group was obviously higher than that in other sites. The percentage of pDC was no significant different in all groups. The expression level of CD86 in all groups was higher than that of CD80, the expression level of CD80 was lower in mDC and pDC of all groups, but there was no obvious difference in all sites. The CD86 expression in all site of refractory group was higher than that in newly diagnosed and effective treatment groups, while the CD86 expression of mDC in spleen of newly diagnosed group obviously higher than that in other sites. It is concluded that the distribution abnormality of mDC and pDC exists in ITP patients, the mDC are more accumulated in spleen, and differentiation of mDC to maturity is more obvious in spleen, spleen-derived mDC significantly express CD86, spleen-derived mDC may play an important role in the pathogenesis of ITP.