Preheat oven to 350 degrees. Grease and flour 2 8-inch or 9-inch round cake pans.
Drain the peaches, reserving the syrup. Add enough water to the syrup to make 1 1/4 cups. In a large bowl, beat cake mix, syrup, oil and eggs until well combined.
Pour batter into prepared pans. Bake at 350 degrees, 27 to 32 minutes for 8-inch pans or 23 to 28 minutes for 9-inch pans. Cool 10 minutes in pan, then remove to wire rack and cool completely.
Cut peaches into bite-sized pieces. Mix yogurt and whipped topping, then fold in peaches. Place 1 layer of cake on serving plate; top with 1/2 of the whipped topping mix. Cover with the second cake layer and frost top with remaining whipped topping mix. Refrigerate about 2 hours before serving.