Paraneoplastic syndromes are defined as a combination of clinical disorders associated with malignant diseases that are caused by the secretion of various substances by the tumor without, however, being caused by the direct growth and infiltration of the primary tumor, or due to the development of distant metastases. Despite the fact that lung cancer represents the number one cause of death from cancer worldwide, the new methods of treatment increase patient survival and the incidence of paraneoplastic syndromes. The most important ones of these are humoral hypercalcemia of malignancy, syndrome of inappropriate antidiuretic hormone, hyponatremia of malignancy, ectopic Cushing's syndrome, carcinoid syndrome, and hypoglycemia and are usually a poor prognostic marker. Early diagnosis of those syndromes is achieved using specific criteria and may lead to early diagnosis of the underlying malignancy. It is essential to treat them with the overriding objective of improving the patients' quality of life.