Irradiation therapy represents one of the mainstay treatment modalities in cutaneous T-cell lymphomas. For the patch and plaque stages UV therapy is mostly used. Among UV light treatment broadband UVB is less effective than narrow band UVB. If these modalities are not sufficient, then PUVA therapy is indicated and might be used in even more advanced stages, including the erythrodermic stage of the disease. For resistant cases and remaining tumors, conventional radiotherapy or electron beam therapy is the treatment of a choice. If the disease is widespread, total skin electron beam radiation gives excellent results. One should not forget the possibility of combining UV therapy with radiotherapy or electron beam radiation, or with chemo- and immunotherapy respectively.