Luminosity distributions of the [O III] λ5007 optical lines (left panel) and at 178 MHz (right panel) for different radio-optical classes from the original 3CR sample studied by Buttiglione et al. (2009, 2010, 2011) and its subset with milliarcsecond observations (3CR-VLBI sample). The filled portion of each histogram bin represents objects with VLBI observations, while the total height of the bin corresponds to the number of sources in the original 3CR sample. The distribution of the VLBI subsample closely follows that of the original sample.