Infrared spectra of mass-selected homoleptic copper carbonyl cluster cations including dinuclear Cu-2(CO)(6)(+) and Cu-2(CO)(7)(+), trinuclear Cu-3(CO)(7)(+), Cu-3(CO)(8)(+), and Cu-3(CO)(9)(+), and tetranuclear Cu-4(CO)(8)(+) are measured via infrared photodissociation spectroscopy in the carbonyl stretching frequency region. The structures are established by comparison of the experimental spectra with simulated spectra derived from density functional calculations. The Cu-2(CO)(6)(+) cation is characterized to have an unbridged D-3d structure with a Cu-Cu half bond. The Cu-2(CO)(7)(+) cation is determined to be a weakly bound complex involving a Cu-2(CO)(6)(+) core ion. The trinuclear Cu-3(CO)(7)(+) and Cu-3(CO)(8)(+) cluster cations are determined to have triangle Cu-3 core structures with C-2 symmetry involving two Cu(CO)(3) groups and one Cu(CO)(x) group (x = 1 or 2). In contrast, the trinudear Cu-3(CO)(9)(+) cluster cation is determined to have an open chain-like (OC)(3)Cu-Cu(CO)(3)-Cu(CO)(3) structure. The tetranuclear Cu-4(CO)(8)(+) cluster cation is characterized to have a tetrahedral Cu-4(+) core structure with all carbonyl groups terminally bonded.