This article deals with the polymerization of the cyclic ketene acetals (CKAs) 2-methylene-4-phenyl-1,3-dioxolane (2), 2-methylene-4-phenyl-1,3-dioxane (3), 4,7-dimethyl-2-methylene-1,3-dioxepane (4), 2-ethylidene-4-phenyl-1,3-dioxolane (5), 2-phenyhnethylene-1,3-dioxolane (6), and 2-isopropylidene-4-phenyl-1,3-dioxolane (7) in the presence of cyanoallene (1). For 2 and 3, the homopolymerization of the CKAs proceeded without; ring opening, and the number-average molecular weights of the obtained polymers depended on the feed ratio of 1. However, the reactions of 1 with 4-7 afforded no polymers but did afford spirocyclic 1 : 1 adducts possessing cyclobutane rings.