The objective of the study was to determine the effect of changes in the raw material composition, as well as in the agglomeration process on water activity of powdered cocoa beverage. The raw materials analyzed were powders (cocoa, sucrose, medium-saccharified maltodextrin, glucose and fructose, and milk); the mixtures from those powders, mixtures were prepared and, next, agglomerated. A basic composition of the mixture contained 20% of cocoa and 80% of sucrose. The change in the composition of raw material consisted in partially or fully replacing the sucrose with the maltodextrin, the mixture of glucose and fructose, or with the powdered milk. The powder ingredients analyzed were characterized by a different water activity. Cocoa showed the lowest value, and sucrose the highest. The mixtures of different composition were characterized by different initial water activity, which depended on the a_w values of individual components and of their per cent content in the mixture. The mixtures containing powdered milk were characterized by the lowest water activity, whereas the products containing 20 % of cocoa and 80 % of sucrose or glucose and of fructose showed the highest water activity. Based on the water activity determined, it was found that the changes in the composition of raw material had a significant effect on the water activity level of the products analyzed. The agglomeration process affected the activity of the tested samples of powdered cocoa beverage to a lesser extent.