Abstract Powerful radio galaxies possess luminous extended emission-line regions. A complete understanding of the properties of these regions is crucial to learn about several important issues, including the origin of the extended gas and the triggering of the nuclear activity. For this, full maps of the kinematics and ionization of the emission-line gas in these sources are required, and integral-field spectroscopy plays an important role in this regard. We review the recent advances in 2-D mapping of the emission-line structures, and then present integral-field spectroscopic observations of three radio galaxies (Coma A, 3C171 and 3C265) which are known to be undergoing jet-cloud interactions at some level. Our images of 3C171 and 3C265 show for the first time that these interactions extend far from the radio axis, indicating that the lateral expansion of the radio jet cocoon has a significant impact on the properties of the emission-line gas in these sources.