The usefulness of newly introduced laboratory parameters such as anti-CCP antibody level (specific „marker” autoantibody in RA) and cartilage oligomeric matrix protein (COMP) level (a very sensitive marker of cartilage degradation), in comparison with RF-IgM level, laboratory disease parameters (ESR, CRP, RBC, Hb and platelet count) and selected clinical parameters (morning stiffness, count of swollen and painful joints, VAS and DAS-28 score) were analyzed in a group of 34 (randomly selected) leflunomide (LFM) treated RA patients – formerly unsuccessfully treated with two DMARD-s (also with methotrexate). Significant differences in ESR rate and platelet count, and also in the case of morning stiffness, count of swollen and painful joints, VAS and DAS-28 scores between the group of LFM treated and untreated were observed. Between analyzed serological parameters such as RF-IgM and anti-CCP antibody level no significant differences between groups (untreated vs LFM treated) were found. Of note, a statistically significant decrease in COMP level, correlated with improvement of the above analyzed clinical parameters, is observed.