RATIONALE: Labyrithine nasal passages, the narrow nasal valve and complex static and dynamic aerodynamics limit traditional intranasal steroids' (INS) ability to effectively deliver medication to superior/ posterior nasal regions. Exhalation delivery systems (EDS) exploit unique characteristics of nasal anatomy and aerodynamics to overcome these limitations and achieve superior/posterior drug delivery. We review published human in vivo gamma-scintigraphy deposition data for conventional INS (C-INS; e.g., Flonase/Nasonex), HFA-based pMDI's (e.g., QNASL/Zetonna), and EDS systems for liquids and powders. METHODS: Four recent gamma-deposition studies comparing different technologies for nasal delivery of topical steroids were included: (1) Conventional INS sprays (Flonase and Nasonex) versus pMDI (QNASL), (2) C-INS (Nasonex) versus pMDI (Zetonna), (3) C-INS versus EDSliquid, (4) C-INS versus EDS-powder and EDS-liquid. Data on regional deposition and clearance was compared. RESULTS: Qualitative deposition differences were large, though variability in segmentation methods prevents quantitative comparisons. In all studies, C-INS consistently deposit primarily anteriorly (in the valve region) with clearance along the nasal floor and little deposition in superior/posterior regions. Both pMDIs (QNASL/Zetonna) show a stationary ''hotspot'' in the non-ciliated vestibule, little delivery to superior/ posterior regions, and minimal clearance. EDS (liquid or powder) produce less deposition in the valve area and broad deposition to superior/posterior segments with a different clearance pattern. CONCLUSIONS: Human imaging data demonstrate poor drug deposition in superior/posterior sites with conventional nasal sprays, and greatly increased deposition throughout upper/posterior nasal passages with an EDS. In CRS, upper/posterior sites, including the middle and upper meatuses (ostiomeatal complex) where sinuses ventilate/drain and polyps originate, are the primary target for treatment.