By allowing an earlier diagnosis and a more exhaustive assessment of extension of the disease, the tomography by emission of positrons (TEP) transforms the care of numerous cancers. At present, (18)F-fluorodesoxyglucose ([(18)F]-FDG) imaging appears as the only one available but new molecular markers are being developed. In the next future they would modify the approach of cancers. In this context, the molecular imaging of the hypoxia and especially the (18)Ffluoromisonidazole TEP ([(18)F]-MISO TEP) can give supplementary information allowing the mapping of hypoxic regions within the tumour. Because of the links, which exist between tumour hypoxia and treatment resistance of very numerous cancers, this information can have an interest, for determination of prognosis as well as for the delineation, volumes to be irradiated. Head and neck tumours are doubtless those for which the literature gives the most elements on the therapeutic impact of tumour hypoxia. Targeted therapies, based on hypoxia, already exist and the contribution of the molecular imaging could be decisive in the evaluation of the impact of such treatment. Molecular imaging of brain tumours remains to be developed. The potential contributions of the [(18)F]-MISO TEP for the care of these patients need to be confirmed. In this context, we propose a review of hypoxia molecular imaging taking as examples head and neck tumours and glioblastomas (GB), two tumours for which hypoxia is one of the key factors to overcome in order to increase therapeutics results.