Natural resources development projects are – and have been for more than 150 years – located in remote rural areas in developing countries, where local level data on community health is notoriously scarce. Health impact assessment (HIA) aims at identifying potential negative health consequences of such projects and providing the initial evidence-base for prevention and mitigation of diseases, injuries and risk factors, as well as promotion of positive effects. An important, but under-systematised early phase of the HIA process is scoping. It aims at organising diverse, often fragmentary, evidence and identifying potential project-related health impacts and underlying data gaps. It is also a key element in defining the terms of reference for the entire assessment. We present novel methodological features for the scoping process, emphasising the evaluation of quality of evidence, and illustrate its use in a contemporary HIA of the Simandou iron ore project in the Republic of Guinea. Assessment of data quality is integrated with specific content information via an analytical framework for the systematic identification of health outcomes and determinants of major concern. A subsequent gap analysis is utilised to assess the need for further baseline data collection and to facilitate the specification of a set of potential key performance indicators and strategies to inform the required evidence-base. We argue that scoping also plays a central role in the design of surveillance systems for longitudinal monitoring of health, equity and wellbeing following project implementation.