A nasal delivery device for delivering a powder or liquid substance to a nasal airway of a subject, comprising: a nosepiece (17 37 57 77) for fitting to a nostril of a subject, the nosepiece (17 37 57 77) including a nozzle (25 45 65 82) through which substance is in use delivered to the nasal airway, and at least one cuff member (27 47 67 80) which is configured such as, when fitted in a nasal cavity of the subject, to engage an inner wall of the nasal cavity of the subject and direct at least a distal end of the nozzle (25 45 65 82) in a direction towards a site in the nasal airway of the subject a delivery unit for delivering substance through the nozzle (25 45 65 82) of the nosepiece (17 37 57 77), wherein a major fraction of the particle size distribution is in the range of from 10 µm to 80 µm and a mouthpiece (19 39 59 79) through which the subject in use exhales to cause closure of the oropharyngeal velum of the subject.
