The photochemically-induced intermolecular C-H bond activation reaction of (HBPz’(3))Rh(CO)(2) (Pz’ = 3,5-dimethylpyrazolyl) has been investigated in various hydrocarbon solutions at 293 K following excitation at 366 and 458 nm. UV-visible and FTIR spectra recorded throughout photolysis illustrate that the dicarbonyl complex can be converted readily to the corresponding (HBPz’(3))Rh(CO)(R)H derivatives at each of the excitation wavelengths. The photochemistry proceeds without interference from secondary photoprocesses or thermal reactions and the reactivity has been measured quantitatively with the determination of absolute quantum efficiencies for intermolecular C-H bond activation (phi(CH)). These measurements indicate that the C-H activation reaction proceeds very efficiently (phi(CH) = 0.13-0.32) on excitation at 366 nm but is much less effective (phi(CH) = 0.0059-0.011) on photolysis at 458 nm for each of the hydrocarbon substrates. The observed dependence of phi(CH) on irradiation wavelength is consistent with different reactivities from two rapidly dissociating low-energy ligand field (LF) excited states and the generation of monocarbonyl (HBPz’(3))Rh(CO) and ligand-dechelated (eta(2)-HBPz’(3))Rh(CO)(2) intermediates upon UV and visible excitation, respectively.