AbstractThe reaction between hexafluoroacetone azine and bis(bicyclo[2.2.1]hept‐5‐en‐2,3‐dicarboximide)s (5 and 6) (dinadimides) (mole ratio 1:1) yields polymers with number‐average molar masses between M̄n = 1700 and M̄n = 5700 depending on the reactants. The possible isomeric structures of the polymers are discussed in detail. From steric considerations which are supported by 13C and 19F NMR spectral data the number of realized isomers is reduced from sixteen to only three (12, 13 and 14). In contrast to these results, hexafluoroacetone azine and dimaleimides do not react to form polymers. This is explained on the basis of a spontaneous rearrangement of the primarily formed 1:1 adduct to 1 H‐pyrazolines.