In a process for the production of dendrimeric or highly-branched polyurethanes (PU) by reacting di- and/or poly-isocyanates with NCO-reactive compounds, at least one of the reactants has functional groups with different reactivity towards the other reactant and the reaction conditions are chosen so that only certain groups react together at each stage. Independent claims are also included for dendrimeric PU and highly-branched PU obtained by this process.