Paraneoplastic syndromes are a group of characteristic clinical syndromes caused by a malignant disease. They are caused by secretion of hormones, functional peptides and cytokines by a primary malignant tumor or are secondary to cross reactivity of tumor cells with normal host cells. This term does not include clinical disorders caused by the direct growth and infiltration of the primary tumor, nor does it include those caused by the development of metastases. Paraneoplastic syndromes are most commonly caused by lung cancer, especially small cell lung cancer. The most frequent paraneoplastic syndromes in patients with malignant lung tumors are endocrine. As the symptoms of these syndromes oftentimes precede the diagnosis of the tumor itself, they play a significant role in early identification of malignant lung tumors. Measuring of secretory components responsible for the development of paraneoplastic syndromes can be used to monitor the clinical course of the disease and the response to cancer treatment. The most common endocrine paraneoplastic sydromes in patients with lung cancer are hypercalcemia of malignancy, syndrome of inappropriate antidiuretic hormone secretion, ectopic Cushing’s syndrome, hypoglycemia and carcinoid syndrome. Specific criteria are used for their diagnosis. They are associated with a poorer prognosis, increased disease burden and a significant decrease in quality of life. Thus, they need to be diagnosed as early as possible and treated adequately and swiftly.