This poster will present an overview of work planned under Phase 4 of the Air Quality Model Evaluation International Initiative (AQMEII). Since its inception in 2009, AQMEII has brought together a total of 37 modeling groups from 17 countries in North America and Europe to conduct coordinated research projects and model inter-comparison exercises aimed at advancing model evaluation practices and informing model development. The focus of Phase 4 is on assessing the ability of regional-scale air quality models to simulate dry and wet deposition of trace gases and aerosols. The poster will present the design of the coordinated model simulations, describe the common emission and boundary condition datasets to be used by all modeling groups, summarize the observational datasets to be used for model evaluation over North America and Europe, and discuss the data infrastructure aspect of the activity. Furthermore, we provide a description of planned analysis methods aimed at quantifying the impact of different process-level deposition algorithms and parameterizations on modeled deposition fields. Finally, we present a roadmap for how output fields generated by AQMEII Phase 4 participants could potentially be used in measurement-model fusion approaches for generating total deposition maps and in ecosystem impact assessment studies.