 Patients with moderate to severe psoriasis who receive standard treatment with Ustekinumab 45 mg at week 0, 4, and every 12 weeks are exposed to UVB-311nm phototherapy on a randomized body half left or right; head exempt 3 x per week for six weeks andor until complete response defined as reduction in PASI to 3. PASI score, patient visual analogue score VAS for therapeutic response, and patient VAS for severity of skin lesions is assessed weekly; and at follow-up visits at month 3, 6, and 12. Paired Wilcoxon testing for differences in PASI and patient VAS scores is done; Fischer exact test is applied to determine differences in complete remission, PASI reduction 90, 75 andor 50 between body sites. 