Combine first 5 ingredients in a medium bowl, stirring well. Gently stir in oranges.
Place 1 lettuce leaf in each pita pocket half. Spoon 3/4 cup chicken salad into each pita half.
Note: Using fat-free mayonnaise instead of regular can help you keep your intake of fat grams down to a healthy level. But remember that even though the mayonnaise is fat-free, it still contains sodium and may need to be limited if you're on a low-sodium diet.