The influence of the simplifications introduced by modeling a molecular structure on the exchange coupling constant is studied for hydroxo-bridged Cu(II) binuclear complexes. This study focuses on the role of the terminal ligands and the counterions. The terminal ligands are responsible for marked changes in the exchange coupling constant, depending on their donor properties, while the counterions have an effect only when directly coordinated to the copper atoms. The study of the magneto-structural correlations for the hydroxo-bridged Cu(II)) binuclear complexes has been extended by analyzing the influence of the Cu-O distance, the effect of the asymmetry at the bridging backbone, and the hinge distortion of the bridge. The increase in the Cu-O distance and the absence of the hinge distortion of the Cu2O2 ring substantially enhance the antiferromagnetic interaction.