In order to obtain a specific polymer adsorbent for atrazine removal, the poly(divinylbenzene) beads were synthesized in radical polymerization using suspension polymerization, and modified with maleic anhydride in Diels-Alder reaction with subsequent base hydrolysis. The porous structure of the adsorbent was obtained by using various mixtures of solvents during the polymerization step; both porous and gel materials were prepared. The objective of the study was to investigate the sorption of atrazine by polymeric adsorbent and thereby evaluate the possibility of the pesticide residues' removal from the aqueous solution. Implementation of carboxylic groups into the polymer structure resulted in obtaining specific interactions between modified poly(divinylbenzene) and atrazine, and therefore, intensification of adsorption was observed. To characterize the hydrogen bond between the herbicide and the adsorbent, quantum mechanics calculations were performed.