An apparatus for helping to protect an occupant of a vehicle includes an airbag configured to be mounted to a seat back of a vehicle seat. The airbag is inflatable between the seat back and an adjacent side structure of the vehicle to one of a first deployed condition in which the airbag is configured for a non-reclined condition of the vehicle seat, and a second deployed condition in which the airbag is configured for a reclined condition of the vehicle seat. The airbag is configured to deploy to the first deployed condition in response to determining a non-reclined condition of the vehicle seat and to the second deployed condition in response to determining a reclined condition of the vehicle seat.