Chitosan (CH) was used as a biocompatible and bioadhesive polymer material to prepare solid dispersions as well as hydrogels loaded with dexamethasone sodium phosphate (DSP), a steroidal anti-inflammatory agent clinically used for treatment of different mouth diseases. Binary solid dispersions at various drug-to-polymer weight ratios were prepared by freeze-drying; their direct compression gave tablets which were characterized for the swelling behaviour and drug release in vitro. Similarly, DSP-loaded hydrogels composed of CH and glycerine were prepared and characterized. CH and DSP showed a good physical compatibility. A slow and prolonged release of the drug was observed in vitro from both kinds of systems. The swelling properties of the polymer seemed to be the main parameter affecting the drug release profile from both tablets and hydrogels at the pH value of mouth. In vivo buccal application of both the systems allowed to obtain a prolonged release of DSP, as compared with a glycerine solution of the drug. From the in vitro swelling studies and in vivo test, the 2:1 CH-DSP solid dispersion in particular can be designated for further investigation.