Aim: The goals of this study were to analyse STAT1, STAT2, STAT3 and STAT5 gene expression profiles in psoriatic arthritis patients in comparison to healthy volunteers (control group) and to determine a potential role of methylation in the regulation of the expression of these genes. Material and method: The material for the determination of the microarray expression profile of the analysed genes was full blood obtained from psoriatic arthritis patients and healthy volunteers. The molecular analysis involved the following stages: RNA extraction, qualitative and quantitative analysis of the extracts and a microarray experiment. The determination of CpG islands was performed using bioinformatic tools: NCBI Reference Sequence and MethPrimer (plus CpG Island Prediction). Results: The analyses were performed using the PL-Grid infrastructure (www.plgrid.pl) with GeneSpring 12.6.1 (p < 0.05). There were differences in the expression profiles of the analysed transcripts between psoriasis patients and controls: STAT1 (FC = +2.88), STAT3 (FC = +2.09), STAT5 (FC = +1.62) and STAT2 (FC = −3.60). For each of these genes, at least one CpG island was detected in the nucleotide sequence. Conclusions: There was an increase in the expression of the analysed genes, except for STAT2, in patients with psoriatic arthritis compared to controls. The results indicate that the expression of these genes may be regulated by DNA methylation. When analysing the methylation pattern, the heterogeneity of cell populations that make up the tissue must be taken into account. Learning about the molecular mechanisms will enable development and implementation of new strategies in pharmacotherapy.