Abstract An analysis of copper–hydrogen interactions of six minima and one transition state on the CuH n potential energy surfaces was done using Atoms in Molecules theory and Natural Bond Orbital approach with UB3LYP/DGDZVP wave functions. We localized one minimum on all CuH n potential energy surfaces (PESs) with the exception of the PES with n = 3. This PES has two symmetrical minima and one transition state. The CuH n complexes with n = 1, 3, and 5 have a monohydride fragment. Those with even number of hydrogens have a dihydride fragment. The remaining H atoms are coordinated as (H 2 ) to CuH or to HCuH. The copper–hydrogen interactions were classified as closed shell ( CS ) and the HH bonds as shared shell using the Laplacian of ρ( r ). When it was considered the | V ( r )|/ G ( r ) ratio, we could split the copper–hydrogen interactions into pure CS and transit CS . Taking into account the magnitude of the H ( r ), the transit CS copper–hydrogen interactions can be divided into dative and metallic . On the other hand, according to the NBO analysis, the copper–H 2 interactions can be classified as synergistic and dative H 2 coordination types. © 2009 Wiley Periodicals, Inc. Int J Quantum Chem, 2010