This paper presents the results of the studies on content levels of methylxanthines: theophylline, theobromine, caffeine, and of phenolic compounds: quercetin, gallic acid, in infusions made of various tea types in a crumbled form. In the experiment, three types of tea, packed in teabags, were used: green, red (Pu-erh), and black tea, manufactured by different companies. Infusions were made of those tea types. The tea infusions differed among each other by the content of the determined components depending on both the brewing time, the type of tea, and the manufacturer of tea. No theophyline was found in the infusions of the teas tested whereas the contents of theobromine, caffeine, gallic acid, and quercetin grew along with the increase in brewing time. The infusions of green teas were characterized by the highest concentration of the compounds indicated, whereas the infusions of black teas – by the lowest concentration of them. The content of quercetin was significantly positively correlated with the content of the gallic acid. Moreover, when comparing the infusions of various tea types among each other, it was found that the majority of significant dependencies among the results of measured content levels of substances determined were in the infusions of black teas. When analysing the infusions of teas with regard to their brewing time, the majority of significant correlations among the compounds investigated were shown in infusions, which were brewed for 6 minutes.