The 17 isomers of the [4]- and [5]phenylenes have been studied with three different computational levels of current-density analysis (CDA) and by calculation of the out-of-plane contribution to nucleus-independent chemical shifts (NICS(πzz)). Current-density maps for these isomeric phenylenes are typically dominated by strong paratropic ring currents in four-membered rings. The relative energies of the isomers, which differ only through the effects of differential strain and aromaticity, were computed at the B3LYP/6-311G* computational level. It was found that the three levels of CDA correlate well among themselves and with NICS(πzz). The latter correlation is improved when the ring sum ΣNICS(πzz) for each isomer is correlated to the ring-current sum ΣJ extracted from CDA. The strain-corrected relative energies of the isomers correlate linearly with ΣNICS(πzz). In particular, the compatibility of different summed quantities with easily computed Hückel-London ring currents suggests a simply calculated measure for dealing with global aromaticity of polycyclic systems.