We analyzed the frequency of single-nucleotide polymorphisms (SNPs) at positions -1053 (rs 2981572), 1380 (rs 2981573), 1462 (rs 2232360), and 3978 (rs 1518108) of the human interleukin-20 (IL-20) gene by tetraprimer ARMS-PCR method. A significant association between patients with psoriasis and the G allele at position -1053 (P<0.05) was established. The pairwise linkage disequilibrium (LD) matrix showed that the nearly complete LD was present within the polymorphisms at positions -1053, 1380, and 1462 of the IL-20 gene. We found that patients with plaque psoriasis had a higher frequency of the HT3 GAA haplotype (P<0.01, OR 2.341, 95% CI: 1.346-4.074) compared to the control group. Likewise, the HT3 GAA haplotype was associated with an increased risk of early-onset psoriasis (P<0.01, OR 2.305, 95% CI: 1.285-4.132), late onset of disease (P<0.01, OR 2.542, 95% CI: 1.266-5.102), familial psoriasis (P<0.02, OR 2.220, 95% CI: 1.249-3.945), and sporadic disease (P<0.01, OR 2.523, 95% CI: 1.390-4.580). Our data indicate that IL-20 gene polymorphisms should have a role in determining susceptibility to plaque-type psoriasis. The possible role of the studied SNPs in the regulation of the expression of IL-20 is unknown yet and needs further studies.