Background. Paraneoplastic syndrome (PNPS) associated with lung cancer (LC) is characterized by rheumatological, dermatological, endocrinological, neurological, nephrologic and other manifestations. PNPS has become an urgent problem of mo dern oncology, but specifics of its course and immediate tumor process have not been investigated enough. The purpose was to estimate the clinical laboratory manifestations of paraneoplastic (neoplasmic) rheumatoid-like arthritis (RLA) within the context of its associations with LC individual signs. Materials and methods. PNPS was detected in 258 (16%) patients with LC and RLA in 41 (16%) cases of PNPS. These patients (29 men and 15 women with an average age of 57 years) made up the main group of this study, and other 217 patients with PNPS (177 men and 40 women with an average age of 59 years) were included into the comparison group. Ano ther control group was formed by 105 patients (22 men and 83 women aged 46 years) with primary rheumatoid arthritis (RA) without LC. Results. LC with RLA is characterized by the accelerated midlobar localization of tumor process (7.4 times more often), its small-cell variant (5.3 times more often) with a low degree of diffe rentiation, the presence of exudative pleurisy, neoplasms germinating into esophagus and metastases growing into the skeleton (pubic, iliac, femoral and sacral bone, jaw and spine). By contrast to the RA, RLA is characterized by oligoarthritis, enthesopathies, seronegativity by the rheumatoid factor and antibodies to cyclic citrulline peptide, less manifested activity and stages of the articular syndrome (by 1/4), higher damage rate of radiocarpal joints (1.8 times), shoulder joints (4.8 times), metacarpal (2.4 times) and metatarsophalangeal (2.5 times) joints, absence of osteousuras, intra-articular chondromic bodies, Steidi and Goff bo dies. Conclusions. Formation of paraneoplastic RLA is observed in every sixth patient with PNPS caused by LC, which is accompanied by specific features not only of tumor process, but also by joint syndrome in comparison with the primary RA. The obtained data necessitate the further investigation in order to develop criteria for early diagnosis of RLA and informative prognostic factors for the further course of LC.