Nasal administration of corticosteroids is the primary method of drug delivery for sinonasal disease treatment since it enables a rapid onset of action and reduced systematic absorption. Disadvantages of conventional liquid formulations led to the development of powder formulations that assure higher local drug concentration, increased stability of the formulation, as well as prolonged drug retention at the nasal mucosa. One type of those systems encompasses polymer-based, drug-loaded microspheres. In this study microspheres were prepared by spray-drying of solution containing sodium dexamethasone phosphate, pectin and hypromellose in 1:1:1 (w/w/w) ratio. Process yield was 65.7 ± 8.7 %, whilst sodium dexamethasone phosphate entrapment efficiency was 94.4 ± 0.4 %. Powder systems containing microspheres and inert carrier (α-lactose monohydrate or mannitol) were prepared by mixing components in 1:1, 1:2, 1:4, 1:7 and 1:9 (w/w) ratios, assuring the homogeneity of the mixtures. Powders containing inert carrier demonstrated improvement of reological properties in comparison with microspheres alone. Powder systems with α-lactose monohydrate had comparable rheological properties to powder systems with mannitol. Swelling properties of the microspheres in simulated nasal fluid were moderate compared to purified water. Addition of an inert carrier increased volume of absorbed medium per milligram of microspheres in the donor compartment, proportionally to the mass fraction of inert carrier. Characterisation of powder systems demonstrated suitability of lactose monohydrate and mannitol as carriers of microspheres for nasal delivery. Systems containing microsperes and inert carrier in weight ratio of 1:9 have proven to be the most suitable for additional in vitro and in vivo tests.