Preheat oven to 375 degrees F (190 degrees C). Grease cookie sheet.
Sift together flour, baking powder and salt.
In a large bowl, cream butter or margarine with sugar. Beat in eggs and lemon flavoring. Mix in milk and flour mixture alternately in three parts, starting with the milk. Gently mix in blueberries.
Drop batter by tablespoons onto prepared sheets 1 1/2 inches apart.
Bake 12 to 15 minutes.