We have analyzed the change of local aromaticity in a series of polyfluorene compounds with the increase of the number of pi-stacked layers. The local aromaticity of the aromatic and non-aromatic rings of polyfluorenes remains unchanged when going from one to four layers of pi-stacked rings according to HOMA, PDI, and FLU aromaticity descriptors. On the contrary, experimental H-1 NMR chemical shifts indicate a reduction of the aromaticity of pi-stacked rings with the increase of the number of layers. Calculated NICS also show a change of aromaticity, but opposite to the tendency given by the H-1 NMR chemical shifts. We show that this increase (decrease) of local aromaticity in superimposed aromatic rings indicated by NICS (H-1 NMR) is not real but the result of the coupling between the magnetic fields generated by the pi-stacked rings. (c) 2006 Elsevier B.V. All rights reserved.