The isoprene oxidation to citraconic anhydride (CA, methylmaleic anhydride) over a V-Ti-O catalyst was studied with steady-state experiments, concentration cycling, fiber-optical in situ diffuse reflectance (DR) VIS spectroscopy and TGA. The results suggest both a reversible deactivation by deposits and a Mars-van Krevelen mechanism. Upon exposure to isoprene, the oxidized catalyst quickly changes its state, presumably by carbon deposition and reduction. This process is significantly faster than the regeneration under oxygen. In addition, the reaction seems to follow a 'rake' mechanism where CA is formed via a sequence of intermediates. The consecutive oxidation of CA leads to a selectivity maximum.