The etiopathogenesis of psoriasis has not been fully elucidated. Nowadays, psoriasis is perceived as a multifactorial disease of genetic origin, in which complex immunological disorders concerning specific and non-specific defense mechanisms play a key role. Researchers emphasize the systemic and inflammatory character of the disease, its autoimmunological aspect and, above all, its dependence on T cells – Th1, Th17 and recently Th22. T cells with type 1 cytokine profile (Th1 and Tc1), Th17 and Th22 lymphocytes, regulatory T cells, NK and NK-T cells, antigen-presenting cells (dendritic cells, including Langerhans cells), keratinocytes, neutrophils, monocytes and makrophages are among the cells that take part in the pathogenesis of psoriasis.