According to statistics every hundredth inhabitant of the planet suffers from epilepsy. Treatment of epilepsy involves taking anticonvulsants, and sometimes lifelong. Typically, each of the groups of drugs used to treat epilepsy acts only for certain attacks, such as partial, generalized myoclonic, tonic and atonic. The dibenzyl amide of malonic acid synthesized under the conditional name dіbamk has shown the ability to counteract different convulsive poisons in experiments on animals, and it is valuable in the pharmacotherapy of epilepsy in case of spasms of various origins. The article presents data on development of the method for determination of related impurities of the synthesis (benzylamine, diethyl malonate) in the dіbamk substance using the method of high-performance liquid chromatography (HPLC). Determination was carried out on a liquid chromatograph with a diode array detector using the chromatographic column with the size of 150 × 4.6 mm filled with octadecylsilyl silica gel for chromatography R Symmetry® C18 with the particle size of 3.5 μm. The chromatographic separation was performed in the gradient elution using the mobile phases of 0.1% solutions of trifluoroacetic acid in water and in acetonitrile on the column filled with octadecylsilyl silica gel. The gradient program for chromatography was as follows: time (min)/%; mobile phase А: 0/90; 5/90→65; 15/65; 25/65→90; 30/90; the time of chromatography-35 min; the flow rate of the mobile phase-1 ml/min, the injection volume-50 μm, the column temperature -25°C; detection was performed at the wavelength of 210 nm. In the chromatographic conditions proposed the complete resolution of dіbamk peaks and peaks of related impurities of the synthesis was achieved.