Improvement in the treatment of head and neck squamous cell carcinomas (HNSCC) is needed. Cancer immunotherapy is emerging as a new cancer treatment option; however, information about the immune profile of tumors is needed to help define predictive biomarkers. In a cohort of 280 HNSCC patients with FFPE tumor blocks and clinicopathologic data we performed immunohistochemistry to investigate the prevalence and tumoural location of specific subsets of tumour infiltrating lymphocytes (TILs) and immune checkpoint regulators PD-L1, IDO1, and LAG3. In a subset of 96 patients, we additionally characterised 594 immune related genes using the Nanostring gene expression platform. Protein and gene expression findings were related to clinicopathologic characteristics and survival parameters. TIL expression was heterogeneous and did not correlate with clinicopathologic or survival outcomes. When stratified by HPV status, we found a significant increase in TILs in HPV positive oropharyngeal squamous cell carcinomas (OSCC) compared to HPV negative OSCC and laryngeal squamous cell carcinomas (LSCC) tumors. In contrast, both high PD-L1 and high IDO1 expression (defined as staining in >5% of cells), observed in 21% (25/119) and 21% (22/104) of LSCC patients respectively, were significantly associated with improved survival. Similarly, in OSCC patients high PD-L1 (31.7%, 33/104) was significantly associated with improved survival. Interestingly, high PD-L1 was rarely observed in HPV negative OSCC (8.6%, 3/32) compared to HPV positive (50%, 33/33) patients. IDO1 results are still to be analysed for OSCC and will be presented at the conference. Gene expression analysis showed that HPV positive OSCC patients exhibit significantly different gene expression profiles to HPV negative patients. We have shown the expression of immune checkpoint inhibitors PD-L1 and IDO1 to be of prognostic value in HNSCC. Further research may identify these factors as predictive of the benefit of emerging immunotherapeutic strategies.