Preheat the oven to 350 degrees F (175 degrees C). Grease and flour a 9 inch tube pan.
In a large bowl, mix together the cake mix, instant pudding, eggs, oil and water for 2 minutes using an electric mixer on medium speed. Stir in the ground walnuts. Pour into the prepared pan.
Bake for 50 to 60 minutes in the preheated oven, or until a toothpick inserted into the cake comes out clean. Cool in the pan before inverting onto a plate to serve.