The study evaluates the performance of density functional theory (DFT) in calculating electronic excitation energies, focusing on local, Rydberg, and intramolecular charge-transfer (CT) excitations. The CAM-B3LYP functional, a Coulomb-attenuated hybrid functional, is found to provide the best overall performance, with no correlation between excitation energy errors and the spatial overlap between occupied and virtual orbitals. In contrast, the generalized gradient approximation (GGA) and hybrid functionals show a clear correlation, indicating significant errors for certain excitations. The study proposes a diagnostic test based on the overlap quantity Λ to judge the reliability of excitation energies from GGA and hybrid functionals. The results highlight the ambiguous nature of charge transfer excitations and provide insights into the accuracy of different DFT functionals in describing these excitations.The study evaluates the performance of density functional theory (DFT) in calculating electronic excitation energies, focusing on local, Rydberg, and intramolecular charge-transfer (CT) excitations. The CAM-B3LYP functional, a Coulomb-attenuated hybrid functional, is found to provide the best overall performance, with no correlation between excitation energy errors and the spatial overlap between occupied and virtual orbitals. In contrast, the generalized gradient approximation (GGA) and hybrid functionals show a clear correlation, indicating significant errors for certain excitations. The study proposes a diagnostic test based on the overlap quantity Λ to judge the reliability of excitation energies from GGA and hybrid functionals. The results highlight the ambiguous nature of charge transfer excitations and provide insights into the accuracy of different DFT functionals in describing these excitations.