Photodynamic therapy (PDT) is a new treatment for head and neck cancer. The principle of the treatment is a photochemical reaction initiated by light activation of a photosensitizer, which causes the death of the exposed tissue. This article presents the modes of action of PDT and the techniques as well as the clinical procedure. A critical review of the literature is also presented, regarding treatment results of the different techniques and indications for treatments. The possibilities for PDT for head and neck cancer in Denmark are mentioned.