Optical dielectric functions epsilon(E) of the (IPA)(4)Cd3Cl10 crystal were measured in the spectral range of fundamental electronic excitations 3.5-10 eV and in the temperature range of 310-400 K containing the phase transition point between the orthorhombic phases Cmce and Pbca. Measurements were performed by spectroscopic ellipsometry with using of synchrotron radiation. Electronic band structure, density of states and dielectric functions epsilon(E) of (IPA)(4)Cd3Cl10 were calculated and analyzed on the basis of the density functional theory. Top valence and bottom conduction bands were found to be formed mainly by the cadmium-chlorine complexes of the crystals. (C) 2013 Elsevier B.V. All rights reserved.