Increasing number of cancer patients are being admitted to the intensive care units and/or resuscitation wards due to rising incidence of solid and/or haematological malignancies together with expanding therapeutic options and improved survival of these individuals. (Potentially) life-threatening cancer-related complications and/or treatment-associated side effects or eventual co-morbidities are the reasons for such admissions. Epidemiology, indication criteria, extension of the treatment, prognosis of the acute disease, and changes applied to the general prognosis as a consequence of the critical illness are all frequent and unanswered intensivists' questions and are being discussed within this review.