Background: Immune checkpoint blockade (ICB) has become a standard pillar of treatment for lung cancer. However, only ̃20% of unselected patients can achieve durable clinical benefits. We performed immunogenomic profiling of tissue specimens from a randomized Phase III trial S1400I on metastatic lung squamous cell carcinoma (SCC) to evaluate if there were factors associated with better prognoses with ICB from single-agent versus combined targeting PD-1/CTLA-4 and evaluate if any differentiated between the treatments. Methods: We utilized FFPE tumor tissue submitted for Lung-MAP screening provided by the SWOG bank. SCC samples from 82 eligible patients treated with combined nivolumab+ipilimumab (N+I) or single agent nivolumab (N) were subjected to multiplex immunofluorescence (mIF, n = 82) and NanoString (ncounter PanCancer Immune Profiling Panel, n = 32). Cell density phenotypes (cells/mm2) were defined using image analysis of staining for cytokeratin, CD3, CD8, granzyme B, CD45RO, FOXP3, PD1, PD-L1, and CD68. Immunogenomic features were associated with response, PFS, and OS derived from data provided by the LungMap team to the CIDC portal. For statistical analyses, non-parametric tests were utilized to assess associations of cell phenotypes versus continuous or categorical variables, and log-rank test analysis was performed to identify cell phenotypes or genes correlated with survival. Results: In both arms higher densities of total CD3+CD45RO+ T cells (P= 0.041), CD3+PD-1+ T cells (P= 0.024) and CD3+CD8+PD-1 T cells in stroma (P= 0.042) and CD3+CD8+GZMB+ T cells in the tumor compartment (P= 0.011) were positively associated with PFS. In the N+I arm but not in the N arm, higher densities of CD3+CD8+GZMB+ T cells in the tumor compartment were associated with better PFS (P= 0.015) and higher densities of stroma CD3+CD8-FOXP3+ T cells with worse OS. Spatial analysis showed that the presence of CD8+GZMB+ T cells close to malignant cells (median, ≤19.27 µm) was associated with better PFS (P= 0.037) in N+I arm and cluster analysis showed low clustering of cells in TMB-high vs. TMB-low tumors (P < 0.01). Gene expression profiling demonstrated that myeloid infiltration, immune recruitment, and inflammation genes were associated with a positive clinical outcome (P< 0.05). In both arms, BLNK,CD163, FCGR2A were associated with better OS (P< 0.01), IRF1 and BLNK were associated with increased PFS (P< 0.01). In the N+I arm but not in the N arm, we observed significantly higher CD45 immune cell scores, including CD8 T cells and neutrophils, in responders versus non-responders. Conclusions: Our findings suggest a potential advantage in PFS and OS with an increased presence of cytotoxic immune cells and genes associated with the recruitment and proliferation of these cell types before therapy.