Aim of this study was to investigate the relationship between the severity of psoriasis and obesity based on the analysis of the visceral fat index and serum levels of tumor necrosis factor-α (TNF-α), interleukin-6 (IL-6) and resistin. The study included 50 patients with psoriasis and 30 subjects in the control group. The measured parameters were height, weight, waist circumference, visceral fat index, and serum levels of TNF-α, IL-6, and resistin. The severity of the disease was evaluated using the psoriasis area and severity index (PASI). Visceral fat index was measured using the method of bioelectrical impedance analysis. Serum levels of TNF-α, IL-6, and resistin were correlated with visceral fat index, and the relationship of all these parameters with psoriasis severity was also analyzed. Patients with psoriasis have a significantly higher body mass index, waist circumference, and visceral fat index compared with the control group. Elevated serum levels of TNF-α, IL-6, and resistin, as well as a correlation with psoriasis severity and visceral fat index was also found in the patient group. Visceral fat index was a better indicator of the relationship between psoriasis severity and obesity than waist circumference and body mass index. We concluded that serum levels of TNF-α, IL-6, and resistin could be useful in assessing psoriasis activity and optimizing therapeutic strategies. It is suggested that visceral fat index should be evaluated in all patients with psoriasis, especially before the decision on systemic therapy.