Preheat oven to 350°F.
Place pita pieces on a baking sheet and lightly spray with olive oil cooking spray.
Bake for 6 minutes or until crisp.
Remove from oven to cool.
Combine chicken, apple, green onion, celery, and sour cream in a medium bowl and stir.
Add salt and pepper to taste.
Place two lettuce leaves on each salad plate to make lettuce "cups" and fill with chicken mixture.
Serve with pita chips. Makes 4 servings.