Process for the continuous preparation of &agr;- and/or &bgr;-ionone or homologous compounds using concentrated sulfuric acid at temperatures from 20 to 90° C., in the presence of organic solvents or diluents with cooling and by subsequent termination of the reaction by hydrolysis of the reaction mixture with water or dilute sulfuric acid, wherein both the cyclization of pseudoionones and the subsequent hydrolysis of the reaction mixture are carried out in a virtually adiabatic reaction in one or more reaction mixing pump(s) which are connected in series and each of which consists essentially of a rotationally symmetrical mixing chamber formed from a peripheral wall and two end walls and of a mixing rotor made of material inert to sulfuric acid and with rotational drive, where the mixing chamber has at least one inlet opening for each component and one outlet opening for the reaction mixture, and annular channels in fluid connection to one another in the end walls, and wherein the heat of the two reactions is in each case partly or wholly removed with the aid of a downstream heat exchanger.