Acetophenones which are substituted on the aromatic ring by fluoroalkyl are prepared in a particularly advantageous, environmentally friendly and effective manner from fluoroalkylanilines and acetaldoxime by preparing from a fluoroalkylaniline a corresponding diazonium salt solution, and reacting this with acetaldoxime in the presence of at least one copper compound, without adding any buffer salts or reducing agents, carrying out the reaction at from 20 to 50° C. and in the presence of halide ions and subsequently heating to a temperature in the range from 70 to 110° C.