HeI photoelectron spectra are reported for a series of methyl-substituted monoketones and diketones based on 2-norbornanone. The effect of methyl substitution, and the inductive effect of a second carbonyl group has been studied. The diketones show a small separation between the two ketone moieties due to a through-bond interaction. Replacement with a thiocarbonyl group permits a comparison of the relative C=S and C=O interactions. The relative merits of the semi-empirical HAM/3 and CNDO/2 methods for such molecules are assessed.