Psoriasis, vitiligo and mycosis fungoides (MF) are the most commondermatological diseases treated by photo(chemo)therapy.Objectives: The aim of our study is to assess which of the routinely usedphoto(chemo)therapeutic modalities might be most effective with less sideeffects in the treatment of psoriasis, vitiligo and MF. We also aimed atdetermining the effect of sex, age, course, duration, extent and clinicalvariant or stage of the disease on achieving good or excellent response withthese modalities. Design: Retrospective analytical study.Patients and methods: The study included 846 patients; 334 patientswith psoriasis, 358 patients with vitiligo and 154 patients with MF who weretreated in the phototherapy unit, Dermatology Department, Kasr El-AiniHospital from September 1997 to September 2006. From them 101 patientsdropped and were excluded from the statistical analysis and studied alone.Data was retrieved from the computer database of the unit and statisticallyanalyzed. Results: In psoriasis, PUVA had statistically significant better results thanboth UVA and BB-UVB at the end of therapy. All predictors had no effecton the response to different phototherapeutic modalities. In vitiligo, PUVAand P-UVB (NB) had statistically significant better results than NB-UVB.Sex, disease course and variant affected the response to some of thephototherapeutic modalities. As for MF, there was no statistical significantdifference in the response to oral PUVA and NB-UVB. Sex, age and diseaseduration affected the response to some of the phototherapeutic modalities. Results: In psoriasis, PUVA had statistically significant better results thanboth UVA and BB-UVB at the end of therapy. All predictors had no effecton the response to different phototherapeutic modalities. In vitiligo, PUVAand P-UVB (NB) had statistically significant better results than NB-UVB.Sex, disease course and variant affected the response to some of thephototherapeutic modalities. As for MF, there was no statistical significantdifference in the response to oral PUVA and NB-UVB. Sex, age and diseaseduration affected the response to some of the phototherapeutic modalities.