Thin films of polyetherimide polymer (Ultem) were prepared and laminated over PPO support films. The Ultem films with thickness ranging from 60 to 815 nm were examined by optical microscopy and atomic force microscopy (AFM) and characterized by gas transport measurements. The Ultem films of 60 and 150 nm showed a slightly higher selectivity for the various gas pairs suggesting the morphology of ultrathin Ultem films must differ from that of the thick films.