A prospective observational study was conducted to analyze to what extent the Psoriasis Area and Severity Index (PASI) is correlated to patient reported outcomes (PRO). Data were collected on 93 outpatients with psoriasis prior to (t1) and after therapy (t2). A higher PASI score was associated with impaired Quality of Life (DLQI), however associations were only weak (R = 0.24 on t1 and R = 0.36 on t2). The average improvement in PASI score was correlated moderately highly with the change of DLQI (R = 0.50) as well as with the PBI (R = 0.45). The threshold values PASI-50 and PASI-75 were likewise positively associated with PRO, but they only incompletely reflect them: about half of the patients with PASI-50 did not see their expectations met (46.9%) or were not satisfied with the condition of the skin after treatment (56.3%). A quarter of these patients experienced no benefits from the therapy. Of the patients with PASI-75, 15.4% were not satisfied with the condition of their skin. In contrast, 36% of patients who did not attain PASI-50 specified a high level of treatment satisfaction. PASI and PRO are associated but based on different concepts. In addition to clinicial severity, patient-defined benefits should be implemented in the evaluation of psoriasis care.