The present invention relates to semi-allogeneic antigen-presenting cells into which proteins and/or peptides or RNA or DNA or cDNA, respectively, encoding said proteins and/or peptides which are overexpressed in tumor cells or which are derived from autologous tumor cells or different tumor cells or different tumor cell lines have been introduced. Furthermore the invention relates to methods for the generation of these semi-allogeneic antigen-presenting cells as well as to the use thereof in the treatment of tumor diseases.