Tumour hypoxia is a recognized cause of treatment failure. Noninvasive methods to quantify distribution and extent of hypoxia remain an unmet clinical need. Quantitation of the longitudinal relaxation rate, R1, using oxygen-enhanced MRI (OE-MRI), can be used to monitor differences in levels of paramagnetic molecular oxygen in plasma. In this study, we report a significantly reduced hyperoxia-induced ΔR1 response in HNSCC in comparison to the healthy lymph nodes, revealed by OE-MRI. Such a reduction can be attributed to regions of impaired tumour vasculature and hypoxia, the presence of which may be linked to a poorer outcome.