Ultraviolet excited photoluminescence of porous silica under vacuum conditions is investigated in samples with different pore diameters. By exciting in the 180–300 nm range, a manifold luminescence activity in the 300–600 nm is found. The reconstructed three-dimensional photoluminescence excitation pattern shows how the distribution of the emissions changes by varying the pore size of the samples. Two different centers are singled out and their relative concentration is suggested to be a function of the pore size of the samples.