Kinetics of photochromic reaction of spiropyran dissolved in a poly(phenylenevinylene) derivative MEH-PPV was studied by optical and impedance spectroscopy. Spiropyran forms metastable, highly polar merocyanine under illumination with light of an appropriate wavelength. Due to charge-dipole interactions, charge carrier traps are formed and affect electrical properties of the polymer matrix, namely capacitance and photoconductivity.