Production of C7H7+ from n-propylbenzene molecular ion has been studied using mass-analyzed ion kinetic energy spectrometry. The kinetic energy release distributions in photodissociation and metastable ion decomposition have been determined. The photodissociation rates have been determined also on a nanosecond time scale. All the experimental data could be explained well with the microcanonical transition-state theories when the reaction was assumed to produce only the benzylium ion. Molecular orbital calculations have been carried out to understand the reason for the dominance of the benzylium channel in this system over the tropylium channel, which is important in the dissociation of smaller alkylbenzene ions.