Phosphite-free polycarbonate molding compositions are provided which contain either a boric acid ester containing oxetane groups, a mixture of a boric acid ester containing oxetane groups and a boron-free oxetane compound or a mixture of a boric acid ester which is free from oxetane groups and a boron-free oxetane compound, in amounts between about 0.01 and 1% by weight, relative to the weight of pure polycarbonate resin. A process for stabilizing phosphite-free polycarbonate compositions to light and heat without impairing their resistance to hydrolysis is also provided by the incorporation of either a boric acid ester containing oxetane groups, a mixture of a boric acid ester containing oxetane groups and a boron-free oxetane compound or a mixture of a boric acid ester which is free from oxetane groups and a boron-free oxetane compound.