Arborio rice and Carnaroli rice are both types of Italian risotto rice, but they have some differences. Arborio rice is shorter and fatter, while Carnaroli rice is longer and thinner. Arborio rice tends to release more starch, resulting in a creamier texture, while Carnaroli rice retains its shape better during cooking. Although they have slight variations, you can generally use them interchangeably in risotto recipes.