The main aim of this work was to study the chemical composition of eighteen ground coffees from different countries and continents with regard to the content of hazardous substances as radioactive elements (40K, 226Ra, 228Ra, 234U, 238U and 137Cs), metals, including heavy metals, aluminum and some microelements (V, Cr, Mn, Fe, Co, Ni, Cu, Zn) as well as substances that have a positive effect on human health and well-being (polyphenols, proteins, fats and caffeine). The tests were carried out before and after the brewing process using the following techniques: gamma and beta spectrometry, a microwave-induced plasma optical emission spectrometer (MIP-OES), gravimetric method, UV–Vis spectrophotometry as well as thin-layer chromatography. The leaching percentage of certain elements/compounds in coffee infusions was also measured. The research showed clear differences between Arabica and Robusta coffees, and also allowed for identifying some differences between Arabica coffees depending on the place of their origin. The results presented can raise consumer awareness and help them make better food choices.