Patients with cancer and pre-existing severe mental disorder, which include moderate to severe depression, bipolar disorder and schizophrenia, are known to have reduced life expectancy and are less likely to get recommended cancer treatment. Barriers at patient-, provider- and system level have been identified, e.g. lack of identification of psychiatric comorbidity, shortage of stabilising psychiatric symptoms and fragmentation of the healthcare system. Patient-centered, interdisciplinary and cross-sectorial healthcare interventions have shown a high potential to improve the cancer care, as argued in this review.