Introduction. Mixed connective tissue disease (MCTD) is a rare autoimmune and distinct disease that includes features of Systemic sclerosis, Systemic lupus erythematosus, Myositis and Rheumatoid Arthritis + the presence of antibody anti U1-ribonucleoprotein (RNP). It is most found in female patients at the mean age of 35-37 years old, sex ratio M/F of 1:10. Patients develop clinical features as: Raynaud’s phenomenon, edema of the hands, arthralgias, myalgias and sclerodactyly with a high titer ANA and anti-U1 RNP. Aim of study. Aim of the study is to represent the clinical and paraclinical particularities of MCTD in patients from Republic of Moldova in comparison with Systemic sclerosis (SSd) and Rheumatoid Arthritis (RA). Methods and materials. This retrospective study included 30 discharge records from the section Artrology and Rheumatology of the Public Medical-Sanitary Institution Clinical Republican Hospital (IMSP SCR) ”Timofei Moşneaga " for the years 2018-2020. In the number of 30 patients, 10 were diagnosed with MCTD (code M351), 10 with SSd (code M340) and the others 10 with RA (code M058). The age range was 40 to 66 years old. Results. The M/F ratio in all 3 sets of patients was 1:10. The average age of all 30 patients was 54 y/o. The disease debuted and the diagnosis was reported: in MCTD at 42/46 y/o, in SSd at 35/45 y/o and 34/42 years old in RA. The most frequent symptoms found in patients diagnosed with MCTD were: arthralgias and morning stiffness in 10 cases, Raynaud’s phenomenon (RP) – 9, myalgia - 7, edema of the hands – 6, fatigue – 6, photosensitivity – 5, esophageal dysmotility and dysphagia – 5, pulmonary fibrosis with shortness of breath was seen in 4 cases. Regarding immunological profile in MCTD, at the moment of evaluation 5 patients manifested elevated ESR (erythrocyte sedimentation rate), high titre of anti U1-RNP antibodies and presence of ANA (Antineutrophil antibody). On the other side, patients with scleroderma are mostly presented with specific features such as: RP-10, sclerodactyly and myalgia –7 cases, telangiectasia and hyperpigmentation of the skin –5. Lung fibrosis and dysphagia were reported more frequently – 8 cases and as for the immunological changes, there were found the presence of anti-centromere antibodies in 6 cases which were also ANA positive. RP was found in 2 cases of RA in comparison with arthralgia/arthritis and morning stiffness that were present in all 10 cases. Unique features in RA were elevated values of CRP (C reactive protein) and RF (rheumatoid factor) in 9 out of the 10 cases as well as signs of thoracolumbar vertebrae involved in the pathological process. Conclusion. To summarize this study, we can conclude that MCTD is indeed a rare disease that affects mostly women with the average age of 42 y/o. During its debut and evolution it can be confused with other overlap syndromes or connective tissue diseases such as scleroderma, RA, SLE, but at the same time MCTD shows milder manifestations of those named above. Key words: mixed connective tissue disease, anti U1-RNP.