Preheat oven to 350°F (175°C). Grease and flour the bottoms only of 2 (8x4-inch) loaf pans.
In a large bowl, mix together the cake mix, oil, eggs, and bananas until well combined. Fold in the chocolate chips. Divide the batter evenly between the prepared pans.
Bake for 43 to 48 minutes, or until a toothpick inserted into the center comes out clean. Cool in the pans for 10 minutes, then use a metal spatula to loosen the edges. Remove from the pans and transfer to a cooling rack. Cool completely, about 1 hour 30 minutes, before slicing. Wrap tightly and store at room temperature.