Cadillac 2008 CTS Owner's Manual page 6

Head Restraints
The vehicle's front seats have adjustable head restraints
in the outboard seating positions.
The vehicle's rear seats have head restraints in the
outboard seating positions, but they are not adjustable.
CAUTION:
{
With head restraints that are not installed and
adjusted properly, there is a greater chance
that occupants will suffer a neck/spinal injury
in a crash. Do not drive until the head
restraints for all occupants are installed and
adjusted properly.
1-2
Adjust the head restraint so that the top of the restraint
is at the same height as the top of the occupant's
head. This position reduces the chance of a neck injury
in a crash.