An apparatus for helping to protect an occupant of a vehicle includes a curtain airbag inflatable from a stored condition adjacent a roof of the vehicle to a deployed condition in which the curtain airbag is positioned between a side structure of the vehicle and the vehicle occupant. A tensioner is positioned adjacent to the vehicle roof and spaced inboard from the vehicle side structure. A tether has a first end portion connected to the tensioner and a second end portion connected to the curtain airbag. The tensioner is configured to pay-out and/or retract the tether. The tensioner is configured to control pay-out and/or retraction of the tether to control deployment of the curtain airbag and/or to control movement of the curtain airbag once deployed.