Background and aim: Psoriasis is a dermatologic disease which not only involves the patient physically, but also affects patient's quality of life. Due to its life time duration and psychologic burden, we decided to evaluate patient's quality of life using psoriasis disability index (PDI). Materials and methods: From August 2006 till March 2007, 80 patients referring to Imam-Reza dermatology clinic completed the PDI questionnaire and a demographic questionnaire. Collected data were analyzed by t-test, one way ANOVA tests using SPSS software. Results: 46.2% of patients were male and 53.8% female. The mean age of patients was 40.2 years. 10% had positive family history of psoriasis. 47.5% had a history of hospitalization. 41.3% had articular and 53.8% had nail involvement. Mean morbidity duration was 12.6 years and mean PDI score was 17.4±10 (maximum and minimum scores: 37 and 1 respectively). There was significant difference in mean PDI score in groups considering age, sex, education, location, duration and extent of disease, hospitalization history, nail involvement and type of treatment. Most disability was seen in the treatment field (both sexes) and occupation /school (men) and least disability was seen in individual relationships.Discussion: Psoriasis can reduce the patient's quality of life and satisfaction severely. Therefore supportive strategies can improve their quality of life.