Paraneoplastic syndromes are frequently detected in many small cell lung cancer (SCLC) patients. In the present paper we report 2 cases of patients diagnosed with SCLC, in whom 2 distinct endocrine paraneoplastic syndromes were identified during diagnosis. In the first patient, severe hyponatremia and renal sodium loss with inappropriate antidiuresis was found during routine laboratory tests. Serum antidiuretic hormone (ADH) level was within normal limits, but the atrial natriuretic peptide (ANP) level was elevated. The second case presented with severe hypercalcemia secondary to an excessive parathormone (PTH) secretion. We discuss the 2 cases and review the literature.