Background and Design: Psoriasis is a chronic, T cell mediated hyperproliferative skin disease. Leptin is an adipokine that stimulates Th1 immune response while suppressing Th2 immune response. Because that leptin plays an important role in the T cell immunity, it is aimed to investigate the relation between psoriasis and leptin and whether leptin plays a role in the immunopathogenesis of psoriasis in the present study. Mateiral and Method: Serum leptin, interleukin (IL)-1 beta, IL-6, IL-8, TNF-alpha and nitric oxide (NO) levels were measured in 54 psoriatic patients and age, sex and body mass index matched 50 healthy control subjects. Results: The mean serum leptin concentration was not statistically different in psoriatic patients compared with the controls (p=0.568). Serum leptin levels were not correlated with PASI score, duration and clinical type of the disease as well as IL-1 beta, IL-6, IL-8, TNF-alpha and NO levels. IL-8 and TNF-alpha levels were significantly higher in patients with psoriasis than healthy control subjects (p=0.002 and p=0,020 respectively). The mean serum IL-1 beta, IL-6 and NO levels were not statistically different in patients when compared with control subjects. Conclusion: These results showed that leptin may not play a significant role in the immunopathogenesis of psoriasis and leptin could not be accepted as a marker to assess severity of the disease. (Turkderm 2009; 43: 48-52)