Decreased number of CD4CD25 T cells might be one of the mechanisms that cause immune regulation dysfunction in ITP and the count of CD4CD25 T cells is considered to be related to the severity of ITP, as these cells were significantly decreased in the active phase of the disease and increased in the patients at the complete remission phase. Therefore, count of CD4CD25 T cells might be a helpful diagnostic predictor of onset and improvement of ITP in children. Finally, it is suggested that these cells may have therapeutic implications that need further clarification.