The invention relates to an inhaler spacer (1) comprising an inlet (2) for connection to an inhaler and an outlet (4) through which a user can inhale. The inhaler spacer (1) comprises a duct (6) extending between the inlet (2) and the outlet (4). The duct (6) is defined by a wall (8) which extends around a first axis (10) and comprises a diffuser portion (12) extending along the first axis away from the inlet. The wall (8) of the duct (6) in at least apart of the diffuser portion curves outwardly away from the first axis with increasing distance away from the inlet such that the cross sectional area of the diffuser portion perpendicular to the first axis increases with increased distance from the inlet along the first axis.
