The present invention relates to the prediction of responsiveness to cancer immunotherapy of a subject based on the T-cell composition of the subject, and a therapeutic method using cancer immunotherapy based on the prediction. The present invention also provides a method for improving or maintaining responsiveness to cancer immunotherapy of a subject. Responsiveness to cancer immunotherapy is predict by determining a relative value of a CD4+ T-cell subpopulation, dendritic cell subpopulation, and/or CD8+ T-cell subpopulation correlated with a dendritic cell stimulation in an anti-tumor immune response in a sample derived from a subject. A composition for treating or preventing cancer comprising cells such as CD62LlowCD4+ T-cells is also provided.