Silsesquioxane derivatives widely used as polymer modifiers and catalytic supports have many interesting features making them potential nanocarriers in biomedicine. Two alternative synthetic routes were described, leading to the conjugates of functional POSS structures: octa(3-chloroammoniumpropyl)silsesquioxane and octa(carboxydecylthioethyl)silsesquioxane with anticancer drugs – anthracyclines.