The C-40 xanthophylls zeaxanthin and astaxanthin were confirmed to form radical cations, Car^· , in the electron-accepting solvent chloroform by direct excitation using subpicosecond time-resolved absorption spectroscopy in combination with spectroelectrochemical determination of the near-infrared absorption of Car^· . For the singlets, the S₂(1B_u ) state and most likely the S_x(3A_g⁻) state directly eject electrons to chloroform leading to the rapid formation of Car^· on a timescale of ∼100 fs; the lowest-lying S₁(2A_g⁻) state, however, remains inactive. Standard reduction potential for Car^· was determined by cyclic voltametry to have the value 0.63 V for zeaxanthin and 0.75 V for astaxanthin from which excited state potentials were calculated, which confirmed the reactivity toward radical cation formation. On the other hand, Car^· formation from the lowest triplet excited state T₁ populated through anthracene sensitization is mediated by a precursor suggested to be a solute–solvent complex detected with broad near-infrared absorption to the shorter wavelength side of the characteristic Car^· absorption. However, ground state carotenoids are able to react with a secondary solvent radical to yield Car^· , a process occurring within 16 μs for zeaxanthin and within 21 μs for astaxanthin. Among the two xanthophylls together with lycopene and β-carotene, all having 11 conjugated double bonds, zeaxanthin ranks with the highest reactivity in forming Car^· from either the S₂(1B_u ) or the ground state. The effects of substituent groups on the reactivity are discussed.