Abstract The title hydrogenation catalyzed by nickel (II) 2, 4-pentanedionate- triethylaluminium system has been studied with the use of combination of initial rate measurements with time changes of product distribution. It was found that the hydrogenation of methyl (9Z, 12Z)-octadecadienoate is first order in the octadecadienoate. Similar results were obtained also for (9Z, 12Z, 15Z)-octadecatrienoate. The course of both reactions has ...