Comorbidity is very common among those with cancer. This project aims to increase our understanding of why Maori with cancer in New Zealand have poorer survival rates compared with non-Maori. We will investigate whether Maori patients with comorbidity receive less quantity or quality of treatment than non-Maori. We will use routine health records and other data sources to gather relevant information including stage at diagnosis, socioeconomic position, and region/ rurality. We will use statistical analyses to understand the way that comorbidity, treatment and ethnicity interact to influence survival for different cancers. We are working in explicit partnership with Maori, clinicians, health service managers and policy makers throughout the project. We will evaluate a range of interventions at both clinical and policy levels aimed at improving outcomes for Maori patients with cancer.