Acute respiratory failure (ARF) is frequent and often fatal in patients with a malignancy. However, there is not one type of "oncology patient", and it's high time that both clinical management and further studies consider specific populations rather than the heterogeneous and artificial group of "cancer patients". This individual-based approach will allow a relevant use of the numerous non invasive diagnostic tools developed during the past years: high resolution tomodensitometry, echocardiography, urine or serum antigen assays, polymerase chain reaction, serum biomarkers etc. These non invasive tools have reduced but not weakened the value of fiberoptic bronchoscopy and bronchoalveolar lavage: some subsets of patients may always benefit from this technique, particularly when new protective strategies such as non invasive mechanical ventilation and target-controlled infusion of sedative drugs are used. The present review focuses on the personalised approach required in "oncology patients" with ARF, based on first identifying the pattern of immunodeficiency, then listing the most probable hypotheses in the light of clinical and radiological findings in order to, finally, select the most accurate diagnostic tools.