Preheat oven to 350 degrees. Line a cupcake pan with 12 paper baking cups. In a medium mixing bowl stir together, flour, baking powder, baking soda, and salt, set aside.
In a large mixing bowl with an electric mixer on medium speed cream butter and sugar until fluffy. Beat in bananas. Beat in eggs, one at a time, then vanilla. On low speed gradually add flour mixture alternating with milk and beat until blended.
Divide batter evenly between baking cups. Bake until toothpick inserted into the center comes out clean, about 25 minutes. Cool cupcakes in pan for 10 minutes. Transfer cupcakes to a cooling rack to cool completley.