Abstract: Ultrathin layers of organic polymers or organic-inorganic hybrid polymers are deposited onto a substrate using molecular layer deposition methods. The process uses vapor phase materials which contain a first functional group and react only monofunctionally at the surface to add a unit to the polymer chain. The vapor phase reactant in addition has a second functional group, which is different from the first functional group, or a blocked, masked or protected functional group, or else has a precursor to such a functional group.