Objective: To report the impact of ustekinumab on quality of life(QOL)in psoriasis. Methods: PHOENIX 2 was a multicenter,randomized, double-blind, placebo-controlled, trial in which 1230 psoriasis patients were randomized to receive subcutaneously administered ustekinumab(45or 90mg 4 weeks apart, then q12 weeks thereafter) or placebo. Patients changed to receive 45 or 90mg ustekinumab at Weeks 12 and 16. Impact on QOL, anxiety, depression, job performance, and work productivity were assessed using the Dermatology Life Quality Index (DLQI), Hospital Anxiety and Depression Scale (HADS), and Work Limitations Questionnaire(WLQ). Results: DLQI improvements from baseline were apparent by Week 4 (6.9 for 45mg and 7.0 for 90mg versus 1.4 for placebo; each p<0.001 versus placebo). At Week 12, improvement in DLQI was 9.3 and 10.0 in the 45 and 90mg groups, compared to 0.5 for placebo(each p<0.001 versus placebo). DLQI improvement was maintained through Week 24 (9.5 in 45mg group and 10.3 in 90mg group). Patients randomized to placebo experienced improvements in DLQI 12 weeks after changing to ustekinumab. At Week 12, 36.7%, and 39.1% of patients receiving 45 and 90mg, achieved a DLQI score of 0, indicating no impact of the disease on patients' QOL, compared with 1.0% receiving placebo(each p<0.001 versus placebo). At Week 12, 71.8% of patients receiving 45mg and 76.9% of those receiving 90mg experienced a reduction of 5 points in DLQI score, signifying an important difference, compared with 21.4% for placebo (each p<0.001 versus placebo). All DLQI scores improved from baseline to Week 12 in each active treatment group compared with placebo(each p<0.001 versus placebo). Improvements were observed in clinical parameters, HADS, and WLQ. Conclusion: Ustekinumab resulted in significant and clinically meaningful improvements in QOL within 1 month after starting treatment; improvements at Week 12 were maintained through Week 24. Improvements were also observed in anxiety, depression, and work limitations.