In recent years, the production, distribution and consumption of so-called new psychoactive substances, such as synthetic cannabinoids, synthetic cathinones, and phenethylamines, have increased worldwide. The present work reports the identification of such substances found in samples of blotter papers that were seized in the city of Bogotá in accordance with the analytical method implemented in the chemistry laboratories of the Attorney General of Colombia. Using gas chromatography coupled to a selective mass ion trap detector, the presence of phenethylamine derivatives, mainly from the 2,5-dimethoxy-N-(2-methoxybenzyl) phenethylamine series, was detected. Among them, 2-(4-chloro-2,5-dimethoxy-N-(2-methoxybenzyl)) phenethylamine, 2-(4-bromo-2,5-dimethoxy-N-(2-methoxybenzyl)) phenethylamine, and 2-(4-iodo-2,5-dimethoxy-N-(2-methoxybenzyl)) phenethylamine (m/z 150, 121, 91) were prevalent. The 2,5-dimethoxy-N-(2-methoxybenzyl) phenethylamine series derivatives correspond to proved powerful hallucinogens that have not yet been subjected to international control and supervision.