Empirical data is presented to describe the relationship between the fluorescence lifetimes (τf) and the position of substituents on the parent molecule, Phenyl-N-Methylcarbamate. The fluorescence lifetimes are determined using time correlated single photon counting technique1. It is found that increasing lifetimes with position of substitution follows the order, meta > para > ortho in the case of mono-alkyl substituted carbamates. Also, the results below indicate that the long fluorescence lifetime of 4-Dimethylamino-3,5-Xylyl-N-Methylcarbamate, τf108 ns2originates from an n-II* lowest excited state and not the usual II-II* lowest excited states of the other N-Methylcarbamates studied.