The effect of the structure of allyl ethers used as built-in monomers of unsaturated polyester resins on the properties of the coatings obtained have been studied. It was found that high hardness of the coatings cured in air using photoinitiators was achieved for the resins with polyfunctional allyl ether monomers incorporated into polyester molecules as the end groups or as the pendant geminal groups. The influence of the presence of a cobalt organic salt on the hardness of the coating from unsaturated resins has also been studied. The extent of crosslinking for the copolymerization of fumaric esters with allyl ethers in air increases, and a smaller amount of photoinitiator may be used when cobalt (II) naphthenate is present in the resin. The results are discussed in terms of the oxidation of allyl ethers and redox cleavage of peroxides formed, leading to an increase in the rate of copolymerization of allyl ethers with fumarate esters.