The e.p.r . spectrum of Cu2+ doped into single crystals of K2Pt(NO2)4 is reported. In contrast to the host lattice, which contains four nitrogen-bonded nitrite groups, superhyperfine structure due to coupling with the nitrogen nuclear spins suggests that the guest Cu(NO2)42- complex contains two nitrites bonded through nitrogen, and two coordinated through oxygens probably asymmetrically chelated . The likely structure and orientation of the copper(II) complex is discussed, and the g and A tensors are interpreted in terms of the ground-state wavefunction parameters.