Solid-state nuclear magnetic resonance (NMR) relaxation studies were performed on Kapton H polyimide films in order to determine the location of water absorption within the polymer lattice and its effects on the microdomain properties of the polymer. Carbon spin lattice relaxation (13CT1), spin lattice relaxation in the rotating frame (T1rho), and inversion recovery cross polarization (IRCP) experiments were performed to analyze wet and dry Kapton films and films exposed to D2O. The conventional pulse sequences for these experiments were modified with a TOSS acquisition sequence in order to remove spinning side bands from the C-13-NMR spectra. The data indicates that the water molecules aggregate near the carbonyl group of the imide ring and are most probably bound via hydrogen bonding. Additionally the water molecules plasticize the polymer network by increasing the amplitude of low-frequency motions.