In vitro - in vivo correlation (IVIVC) allows prediction of in vivo drug deposition from a nasally inhaled drug based on in vitro drug measurements. In vitro measurements include physical particle characterization and, more recently, deposition studies using anatomical models. Currently, there is a lack of IVIVC for deposition measurements in anatomical models, especially for deposition patterns in various nasal cavity regions. Therefore, improvement of in vitro and in vivo measurement methods and knowledge about nasal deposition mechanisms should help IVIVC in the future.