While pillow choice is largely a matter of personal preference, the best pillow for neck pain is one that supports and contours to the neck's shape. While a bad pillow will not directly cause neck pain, it can exacerbate problems such as headaches, neck pain, and shoulder and arm discomfort.
A good pillow should keep the head in "neutral alignment" — sitting squarely on the shoulders and not bent too far back or reaching too far forward. To determine what pillow is best, a person should first think about her sleeping style. Back sleepers need thinner pillows to avoid pushing the head and neck too far forward; side sleepers need firmer pillows to fill the space between the ear and the outside shoulder; and stomach sleepers need very thin, almost flat pillows and may actually be better off tucking a pillow under the stomach to avoid lower back pain. Pillows often stop supplying support when old, and it is recommended they be replaced every 12 to 18 months.