Osteopontin (OPN) is a phosphorylated acidic glycoprotein produced by cells of the immune system, epithelial tissue, smooth muscle cells, osteoblasts, and tumor cells. OPN interacts with integrins and CD44 to enhance Th1 and inhibit Th2 cytokine expression. The involvement of this molecule in the onset of psoriasis has not previously been studied. Here, we demonstrate that OPN is expressed in peripheral blood mononuclear cells and in skin biopsies of psoriatic patients. The study was conducted on 30 patients affected with plaque psoriasis, and on 11 healthy donors. Two blood samples and two skin samples from patients affected with atopic dermatitis were used as control for Th2 typical inflammatory skin disease. The analysis of IL-1β, IFN-γ, **********F-α, IL-8, and ICAM-1 showed the characteristic Th1 pattern in all the psoriatic blood and skin samples analyzed. This study offers an opportunity for understanding inflammation in psoriasis and supports the hypothesis that OPN could represent a potential target for therapeutic intervention in psoriatic patients.