A nasal delivery device for delivering a substance to a nasal cavity of a subject, including: a nosepiece (240) adapted for insertion into a nostril of a subject and a flow path fluidly connected to the nosepiece (240) wherein the nosepiece (240) is expandable and configured such as to expand on generation of a pressure in the flow path, thereby sealing with the nostril of the subject and providing for expansion of the nasal cavity of the subject.
