The photosensitive organic system Poly(Methyl MethAcrylate)/DiMethoxyPhenylAcetophenon (PMMA/DMPA) is studied by real-time holography. Thin film samples (thickness ≃ 50 μm) are prepared by solution deposition on glass substrates using different solvents. Besides this, block samples with a thickness of about 2 mm are investigated. The achieved grating constant varies between 1.1–2 μm using the 363.8 nm UV line of an argon-ion laser. DMPA concentration varies between 0.5–10% and affects the temporal stability of the gratings, dynamics of the diffraction efficiency and the sensitivity of the photopolymer system. The gratings are also characterized by measuring the angular sensitivity. With a functional polymer as a matrix material stable gratings could be obtained.