The current study focuses on the impact of BN doping on the first singlet/triplet excited-states of simple BNdoped polyaromatic hydrocarbons. Our results, obtained on BN-phenanthrenes and other polyaromatichydrocarbons, demonstrate that the BN-doping effect on the first single and triplet excited states of the parental hydrocarbon heavily depends on the electron delocalization between the carbon atoms being replaced. Specifically, it is revealed that dramatic changes occur when single CC-bonds of low-electron-delocalization are replaced. On the other hand, the replacement of CC-bonds of higher electron-delocalization, such as aromatic and/or double-CC-bonds, results in weaker and in some cases negligible variations of the lowest singlet and triplet excited-states.