  We study the narrow-line region (NLR) of six Seyfert-1 and six Seyfert-2
galaxies by means of spatially resolved optical spectroscopy and
photoionization modelling. From spatially resolved spectral diagnostics, we
find a transition between the AGN-excited NLR and the surrounding star-forming
regions, allowing us to determine the NLR size independent of stellar
contamination. CLOUDY photoionization models show that the observed transition
represents a true difference in ionization source and cannot be explained by
variations of physical parameters. The electron density and ionization
parameter decrease with radius indicating that the NLR is photoionized by the
central source only. The velocity field suggests a disky NLR gas distribution.
