Zirconium oxide cluster cations and anions are produced by laser ablation and reacted with CO in a fast flow reactor. The CO adsorption products Zr(x)O(y)CO(+) are observed for most of the generated cationic clusters (Zr(x)O(y)(+) = Zr(2)O(5,6)(+), Zr(3)O(7,8)(+), Zr(4)O(9,10)(+) ...) while only specific anionic systems (Zr(x)O(y)(-) = Zr(3)O(7)(-), Zr(4)O(9)(-) ...) absorb CO to produce Zr(x)O(y)CO(-) . To study how the CO molecule is adsorbed on the clusters, the Zr(x)O(y)CO(+/-) products are mass-selected by a time-of-flight mass spectrometer (TOF-MS) and collided with a crossed helium beam. The fragment ions from collision-induced dissociation (CID) are detected by a secondary TOF-MS. Loss of CO and CO(2) is observed upon the collision of the helium beam with Zr(x)O(y)CO(+) and Zr(x)O(2x+1)CO(-) respectively. Density functional theory calculations indicate that oxidative and nonoxidative adsorption of CO takes place over Zr(3)O(7)(-) and Zr(3)O(7)(+), respectively. This is consistent with the CID experiments.