The objective of this study was to assess the comparative effectiveness of intensity-modulated radiation therapy (IMRT), conformal and two-dimensional radiation therapy, proton beam, and carbon ion therapy in terms of tumor control and survival on the one hand and adverse events and quality of life on the other in irradiated head and neck cancer patients. A search of the literature was performed. At a given time, innovative techniques in radiation therapy may appear superior to routine irradiation techniques and clinical trials may therefore be considered unethical. IMRT, because of its superiority in terms of dose distributions and potential to preserve the salivary glands, has gradually replaced two-dimensional and conformal irradiation in routine use. The PARSPORT phase III trial is one among the rare trials to randomize two-dimensional and conformal irradiation against IMRT. It showed a 50% reduction in late xerostomia. Similarly, the relevance of clinical trials to prove the superiority of protons compared with photons is highly controversial. Although the expected benefit of particle beam therapy on dose distributions, local control, and quality of life seems sufficient for routine use without phase III trials, it should be noted that new toxicity profiles might be seen as was the case for IMRT (posterior alopecia, anterior mucositis, uncertainties of integral dose, and secondary cancers). Prospective clinical and medico-economic assessment, possibly in phase II trials, is therefore critically needed along with stringent quality assurance programs. Technological advances in radiation therapy clearly provide a benefit for patients despite the lack of level I evidence.