Paraneoplastic autoimmunity can develop in conjunction with almost any malignancy, but its clinical presentations as well as pathogenesis are extremely variable. Autoimmune damage can affect several organ systems: there have been defined neurologic, dermatologic, hematologic, rheumatologic and systemic syndromes. According to pathogenesis, paraneoplastic autoimmunity can evolve either due to central or peripheral tolerance defects or altered self antigeen expression by malignant cells. Paraneoplastic autoimmunity can appear either before of after tumour diagnosis, and can even indicate the localization of a not yet diagnosed malignancy. Autoimmune syndromes can disappear or improve significantly after tumour eradication, however, certain syndromes require immediate immunosuppressive treatment to avoid fatal or irreversible damage. Paraneoplastic autoimmunity can be associated with better prognosis for the underlying tumour or with less metastases, reflecting better control of tumour growth and stronger anti-cancer immunity.