Hypertrophic osteoarthropathy (HOA) is a syndrome that manifests itself by clubbing of fingers, periosteal and osteal neoformation in acral bones and oligo- or polysynovitis. It may occur as primary form (mostly hereditary) or secondary form, associated with various diseases, especially neoplastic or infectious diseases.The purpose of the study was to point out that when the symptoms of HOA occur, it is necessary to search for the primary disease, which is usually represented by tumor.The study reports a case of a patient with symptoms of HOA, pulmonary adenocarcinoma confirmed by histological examination, and with metastases spread into peripheral lymph nodes. The examination of symptomatology of HOA indicated that to pulmonary carcinoma.The medical history of the patient shows that if there is, at an early stage, little attention paid to the fact that HOA represents a paraneoplastic syndrome, cancer is then confirmed later at a more advanced stage. Neglection of this fact delays the primary diagnosis, deteriorates the prognosis and limits the treatment by the extent of the cancerous process.In practice, manifestations of HOA may point to the primary cancerous disease. When the symptomatology of HOA appears, radiograms usually pick up tumours at their early stages, which is important for the prognosis and the strategy of their treatment. The situation was different with the case reported in the study, because the disease was diagnosed at a more advanced stage, which unfavourably affected the prognosis and the treatment of the disease. (Tab. 1, Fig. 4, Ref. 15.)