Lymphoepithelioma-like carcinoma (LELC) of the lung is an undifferentiated carcinoma with prominent lymphoid stroma. We encountered a case of synchronous primary lung cancers of LELC and papillary adenocarcinoma in a 67-year-old Japanese woman. By in situ hybridization, Epstein-Barr virus (EBV) genome was detected in malignant epithelial cells of LELC but not in the papillary adenocarcinoma. Tumor-infiltrating lymphocytes in LELC were predominantly CD8⁺ and T cell intracytoplasmic antigen (TIA-1)⁺ cytotoxic T cells with closely associated with HLA-DR-positive LELC cells by double immunostaining. These data indicate that the exaggerated lymphoid infiltration in and around the EBV-infected carcinoma cells may represent the enhanced tumor immunity, suggesting a better prognostic indicator.