The temperature dependence of the electrical conductivity and Seebeck coefficient of some new organic compounds (derivatives of thiosemicarbazide complexed with nickel cations) are investigated. The measurements have been performed using thin films deposited from the solutions of compounds. All investigated compounds have semiconducting properties. The values of some characteristic parameters (the concentration and mobility of the charge carriers, thermal activation energy of electrical conduction) are determined. The nature of the mechanism of electrical conduction in these organic semiconductors is discussed. (c) 2006 Elsevier B.V. All rights reserved.