A high flow nasal therapy system (1) has a gas supply (2), a nebulizer (12), and a nasal interface (7). There are two branches (11, 10) and a valve (6) linked with the controller, the branches including a first branch (11) for delivery of aerosol and a second branch (10) for delivery of non-aerosolized gas. The controller controls delivery into the branches (11, 10), in which flow is unidirectional in the first and second branches, from the gas supply towards the nasal interface. The first branch (11) includes the nebulizer (12) and a line configured to store a bolus of aerosol during flow through the second branch (10). The valve (6) comprises a Y-junction between the gas inlet on one side and the branches on the other side.
