Morphea is a disease included in the group of scleroderma type autoimmune diseases. Interleukin (IL)-17A may play a role at every stage of its pathogenesis. The study aimed at evaluation of IL-17A and IL-23 (as the main cytokine which is supposed to stimulate and maintain synthesis of IL-17) in pathogenesis of morphea.The studies were performed on 41 blood samples from patients with morphea. Skin was sampled from 29 patients. The evaluation included: (1) expression of IL-17A and IL-23 genes in peripheral blood mononuclear cells (PBMC) using real-time polymerase chain reaction (PCR), (2) plasma concentrations of IL-17A and IL-23 using ELISA, (3) expression of IL-17A and IL-23 genes in skin using real-time PCR.The results of gene expression are expressed as median number of copies per million copies of GAPDH. Higher expression of IL-17A has been demonstrated in PBMC of morphea vs. control group (2630 and 1906 respectively; p = 0.004), accompanied by absence of significant differences in its plasma concentration (10 pg/ml in both groups) and by lowered expression in affected skin (9119 and 19113 respectively; p = 0.036). The results failed to demonstrate elevated IL-23 plasma concentration in morphea vs. control group (5 pg/ml and 6 pg/ml respectively; p = 0.335) or its increased expression in the skin (292 vs. 427; p = 0.383), although we noted its increased expression in PBMC (4419 vs. 808; p < 0.001).BASED ON THE OBSERVED CORRELATIONS WE SUGGEST THAT: (1) IL-17A does not represent a factor which promotes tissue injury in morphea, (2) IL-23 may playa role in pathogenesis of morphea.