Electron paramagnetic resonance of Cu2+-doped catena-trans-bis(N-(2-hydroxyethyl)-ethylenediamine) zinc(II)-tetra-mu-cyanonicelate(II) [Zn(NH2(CH2)(3)NHOH)(2)Ni(CN)(4)] single crystals and powder are examined at room temperature. The spectra show the substitution of the Zn2+ ion with the Cu2+ ion. The crystal field around the Cu2+ ion is nearly axial. There is a single paramagnetic site with g(xx) = 2.073, g(yy) = 2.060, g(zz) = 2.248, A(xx) = 40.5 G, A(yy) = 50.8 G, A(zz) = 172.0 G. The groundstate wave function is an admixture of d(x)(2)-(2)(y) and d(z)(2) states. The optical-absorption studies show two bands at 320 nm (31250 cm(-1)) and 614 nm (16286 cm(-1)), which confirm the axial symmetry. The crystal field parameters and the wave function are determined.