The copolymerization of maleic anhydride (MA), N‐2‐chlorophenyl maleimide (2‐CMI) and N‐α‐naphthyl maleimide (α‐NMI) with styrene (ST) initiated by α‐radiation has been studied. The initial rate of copolymerization depends on the total concentration of the comonomers, and the rate decreases in the series ST/MA > ST/α‐NMI > ST/2‐CMI. The maximum rate occurred at a ratio for which [M2] > [ST]. The rate of formation and the reaction of m 1˙ is greater than m 2˙. The monomer reactivity ratios indicate that the ratio of alternating units decreases in the order ST/MA > ST/α‐NMI > ST/2‐CMI.