Paraneoplastic syndromes are group of conditions that are related to cancer, but not caused directly either by local invasion or metastatic spread. They occur in 5–10% of patients with cancer and their incidence varies depending on the tumour type and tumour stage. Paraneoplastic syndromes are important, because they may be the presenting feature of a disease, can produce treatable symptoms (leading to better life quality), may act as a marker of the therapeutic response. Finally, they may provide meaningful prognostic imformation. The causes of paraneoplastic syndromes are not fully understood. However, two main mechanisms have been identified: the first one is due to inappropriate hormonal or cytokine secretion, while the second is related to the antitumour antibodies production that additionally react with normal tissue elements. Clinically most frequent and important are the following paraneoplastic syndromes: constitutional symptoms (cancer cachexia, fatigue and fever), numerous neurological syndromes (eg. Lambert-Eaton myasthenic syndrome, cerebellar degeneration, retinopathy, encephalomyelitis), haematological disorders (eg. anaemia of chronic disease, neutrophilia, thrombocytosis), disorders of haemostasis (eg. disseminated intravascular coagulation), rheumatic conditions (eg. hypertrophic osteoarthropathy) and multiple skin syndromes (eg. disorders of pigmentation, erythematous conditions). Of particular importance is paraneoplastic origin of several metabolic syndromes (eg. hypercalcaemia and hyponatremia). The underlying mechanisms, clinical picture and management of most important paraneoplastic syndromes are presented in this overview.