Datasets defining emissions of greenhouse gases and air pollutants underpin all model assessments of air quality and climate change. Although often emitted from the same source, the inventories have developed along mostly separate lines. This Opinion presents the case for coordinated development of air pollutant and greenhouse gas emission inventories, which would be an important step towards reliably evaluating the potential co-benefit of air pollution control and climate mitigation. The article discusses the similarities and differences between the two inventories, their historical development and applications, as well as the future challenges of a coordinated development of both. It also makes important recommendations for organizations, compilers, and research groups.