Check the cocoa powder label to determine whether it is natural or Dutch processed.
Compare the color, aroma, and flavor of each type.
Check the recipe's leavening ingredients, especially baking soda and baking powder.
Use natural cocoa powder when the recipe specifically calls for it and relies on its acidity.
Use Dutch processed cocoa when the recipe specifies alkalized cocoa or when its darker color and smoother flavor are desired.
Avoid making a direct substitution in a carefully balanced baked recipe unless you understand how the change may affect the leavening and texture.