BackgroundCharacteristics of health systems almost certainly play some role in the well-documented differences in cancer survival across countries, but which ones are important drivers of these differences is less clear. As part of the International Cancer Benchmarking Partnership (ICBP), we asked what roles leadership and health system capacity play in cancer survival. MethodsWe (i) developed a conceptual (‘logic’) model visualising the components of the cancer care system and the relationships between them; (ii) analysed cancer plans and strategies in 20 ICBP jurisdictions (1995-2018); and (iii) conducted interviews with 79 key informants in 13 jurisdictions to obtain perspectives on how health system factors impact survival. ResultsLeadership emerges as important: political leadership to initiate and maintain progress; intellectual leadership to drive change; clinical leadership to translate policy into action; and coherent visions shared by leaders across each level of the system. The most important aspects of health system capacity identified were primary care providing access to diagnostic evaluation, specialist care providing access to treatment, and the cancer care workforce. Improved infrastructure for diagnosis and treatment was associated with better cancer outcomes in all jurisdictions but was insufficient on its own if staffing was inadequate. Consolidation of services and greater surgical specialisation brought improvements in some jurisdictions if accompanied by reconfigurations of services, in particular the creation of specialist multidisciplinary teams, along with supporting capacity in the wider health system. Staff shortages were commonly cited as reasons why some jurisdictions lagged behind others. ConclusionsContinued progress in cancer outcomes requires strong leadership at all levels of the health system, political commitment to progress strategies, and expertise and engagement by clinicians advising on strategy and making changes on the ground. It also requires sustained strategic investment in plans to deliver and maintain the workforce engaged in cancer care and in the infrastructure on which they depend. Strategic plans must recognise that systems for cancer care do not work in isolation from the rest of the health system.