Electron paramagnetic resonance spectra of Cu2+ -doped [Zn(picol)(2)(H2O)(2)].2H(2)O (C12H18N2O8Zn) single crystals which were taken at room temperature are discussed. It was found from the analysis of the EPR data that the Cu2+ ions substitute for magnetically inequivalent Zn2+ ions. Two magnetically inequivalent sites for Cu2+ were observed. The spin Hamiltonian parameters were determined and thus, the ground state wave functions of Cu2+ ions in two sites were constructed. (c) 2007 Published by Elsevier B.V.