One of the major secondary metabolite which is found in coffee, tea, guarana, etc. is caffeine. Caffeine has an important role in the plant, because it protects the plant against herbivores and patogens. The purpose of our study was to check, what is the content of caffeine in different plant sources and whether caffeine could be used as a natural pesticide. In our case we chose corn bug (Sitophilus zeamais Motschulsky) and a green peach aphid (Myzus persicae Sulzer). From various natural resources such as green and black tea, mate tea, Barcaffe coffee, instant coffee Nescafe and Deadwish coffee we extracted caffeine and various phenolic substances. The highest caffeine content was in the instant coffee Nescafe, while the lowest content was in mate tea. For all preparations, the highest caffeine content was obtained by extraction with water, and the lowest was obtained by extraction with methanol. The content of caffeine was highest for all preparations in the first extraction. Then we tested the effects of these preparations on selected pests. Results showed that caffeine did not have a high impact on the mortality of both pests but at least it negatively influenced, their reproduction and the further development of offsprings.