The present invention relates to a method for the production of substituted trifluoroethylenes, in which a compound of the formula (II) in which R is C1-C6-alkyl optionally substituted by carboxyl, halogen, C1-C6-alkoxy, C1-C6-alkoxycarbonyl or C1-C4-alkylcarbonyloxy or is the grouping in which R′ and R″ are, independently of one another, hydrogen or C1-C6-alkyl or the two, together with the nitrogen atom to which they are bonded, are saturated cycloalkyl with 3 to 5 carbon atoms, in which a ring member is optionally replaced by oxygen or sulfur and which is optionally substituted by one to four C1-C4-alkyl, trifluoromethyl or C1-C4-alkoxy, and Hal is chlorine, bromine or iodine, is brought into contact with a dehalogenating agent in a polyol or its ethers.