Methods and apparatuses for desulfurizing hydrocarbon streams are provided herein. In one embodiment, a method for desulfurizing a hydrocarbon stream includes separating the hydrocarbon stream into a heavier fraction and a lighter fraction. The heavier fraction includes a relatively higher amount of lower octane mono-unsaturates and the lighter fraction includes a relatively higher amount of higher octane mono-unsaturates. The method further includes hydrodesulfurizing the heavier fraction in a first hydrodesulfurization zone and hydrodesulfurizing the lighter fraction in a second hydrodesulfurization zone. Further, the method forms a hydrodesulfurized stream from the heavier fraction and the lighter fraction.