The element effect of halogens has provided crucial mechanistic evidence for many organic reactions, but it has not been determined for nucleophilic aromatic photosubstitutions. We have remedied this deficiency. Ultraviolet irradiation of 4-nitroanisole and 2-halo-4-nitroanisoles (halogen = F, Cl, Br, I) in 1:2 acetonitrile:water solution containing cyanide ion causes mainly displacement of halogen and nitro groups by cyanide ion, and some formation of a heretofore unknown stable nitronate ion. The latter shows that cyanide ion retains its attachment to a ring carbon after attack, i.e. that it is “sticky”. We have determined the product distributions from these reactions, the Stern-Volmer plots for dependence of reciprocal quantum yield on reciprocal nucleophile concentration, the triplet lifetime and quantum yield of intersystem crossing of each of the nitrophenyl ethers. The bimolecular rate constants for attack of cyanide ion on the triplets at the various ring positions are calculated from these data. The reactions are very fast. The rate constant for attack of cyanide ion at the fluoro position of triplet 2-fluoro-4-nitroanisole (2.4 x 109 M-1 sec-1) is half of the diffusion rate constant. The relative rates for attack by cyanide ion on the halogen-bearing carbon are 26:2:2:1 for F, Cl, Br, and I, respectively. The relative rates of photodisplacement of halogens are inverse to halogen leaving group abilities (element effects) in SN2 and E2 mechanisms and parallel to the element effect for ground state nucleophilic aromatic substitutions by comparable nucleophiles. This implies direct formation of a sigma complex from the triplet.