Paraneoplastic syndromes of central nervous system are rare neurologic syndromes caused by cancer but not secondary to metastases. The physiopathologic mechanisms underlying these syndromes are still under debate. We report the biological and clinical features of the most frequent paraneoplastic syndromes involving the central nervous system. Their early clinical identification might be an useful marker of an otherwise unknown visceral malignancy. Furthermore, they might also be suggestive for the particular type of cancer present. Once, therefore, the diagnosis of these paraneoplastic syndromes has been established, an appropriate evaluation for the asymptomatic neoplasm in cancer-free individuals or investigation for the malignancy recurrences in oncologic patients might be performed.