Objectives: People with severe mental illness (SMI) are at extreme risk of being stigmatized and to receive poor quality physical care. It has been demonstrated that they have higher morbidity and poorer prognosis of several medical diseases than the general population, with an at least 10-20-year reduction in life expectancy. Methods: A special issue of Psycho-Oncology focusing on cancer care among patients affected by SMI was called by the Editorial Board of the journal, with the aim to explore cancer health disparities and inequalities among people with SMI, mortality from cancer, problems of communication between multidisciplinary oncology and psychiatric teams and need for more structured intervention (i.e., screening, prevention, treatment). Results: Authors from eight countries contributed. The problem of stigma and barriers to cancer care provision for patients with SMI were studied (e.g., the complex nature of SMI and healthcare providers' misunderstanding of SMI). Key barriers were related to both patients, clinicians and institutional problems, such as fragmentation of care. A higher mortality from cancer and poor knowledge about cancer risk-factors was shown in patients with SMI. Models of intervention were also proposed. Conclusions: Several conclusions have been recommended by the authors, such as the need for guidelines and clinical procedures specific for cancer care in mental health settings; large-scale studies to address the disparities of care in people with SMI; a larger vision of psychosocial oncology as the facilitator of the liaison between oncology and psychiatry.