A nasal delivery device for and method of delivering substance to the middle meatus in a nasal cavity of a subject in the treatment of a condition, in particular an inflammatory or infectious condition, thereof, the delivery device comprising: a nosepiece unit (17) including a nosepiece (20) for fitting to a nostril of a subject and a nozzle (25) through which substance is in use delivered to the respective nasal cavity; and a delivery unit (29) for delivering substance through the nozzle of the nosepiece; wherein the delivery device is configured to provide for deposition of a significant fraction of the delivered dose on, around and in the vicinity of the middle meatus.