The purpose of this study was to assess the properties of CD4 + CD25 high/low/negative T cell subsets and analyze their relation with dendritic cells (DCs) in patients with hepatocelluar carcinoma (HCC). In HCC patients, the prevalence of CD45RO + cells in CD4 + CD25 high T cells was increased and associated with higher frequencies of plasmacytoid DCs. Larger proportions of this T cell subset were detected in the patients with larger tumor burdens. These results suggest that increased frequencies of the CD45RO + subset in CD4 + CD25 high Tregs in HCC patients may establish the immunosuppressive environment cooperatively with tolerogenic plasmacytoid DCs to promote disease progression of liver cancer.