Psoriasis can significantly affect the physical, psychological, and social aspects of a patient's life. Many studies have evaluated the effects of psoriasis on quality of life (QoL), but results in many cases are contradictory. This study was conducted to assess the relationships between the characteristics of psoriasis (cutaneous severity, arthropathy, treatment) and comorbidities with QoL and to determine which factors have a major influence. We assessed demographic data, the severity of cutaneous involvement, psoriasis treatment, presence of arthropathy, psoriasis duration, smoking status, alcohol intake, and the presence of comorbidities. Concomitant diseases were evaluated using the Charlson Comorbidity Index and the National Cholesterol Education Program Adult Treatment Panel III (ATP-III) criteria for metabolic syndrome. Quality of life was assessed using the Dermatology Life Quality Index (DLQI). Multivariate analysis showed that factors associated with QoL impairment included gender (women experienced greater impact: odds ratio [OR] 2.85, 95% confidence interval [CI] 1.48-5.49; P=0.002); psoriasis duration (patients with longer durations of psoriasis and psoriasis treatment experienced less impairment: OR 0.96, 95% CI 0.94-0.99; P=0.004); and treatment type (impact was lower in patients receiving biologic drugs than in those using topical treatment [OR 3.15, 95% CI 1.50-6.62; P=0.002] and in those using biologics compared with those using conventional systemic treatment [OR 2.23, 95% CI 0.98-5.05; P=0.053]). Psoriasis severity measured according to scores on the Psoriasis Area and Severity Index (PASI) and body surface area affected was not related to QoL impairment. Comorbidities were associated with impaired QoL in the univariate analysis but not after adjusting for other covariates. Factors associated with greater impairment of QoL were gender, psoriasis duration, and type of treatment. Patients receiving systemic and biologic therapies reported better QoL.