Comparison of the molecular gas properties, part I. Left panels: scaling relations of the molecular gas mass (M_H2) as a function of the host-galaxy stellar mass (M_⋆; top row) and SFR (bottom row); in the central panel, we show the molecular gas fraction (f_mol = M_H2/M_⋆) as a function of M_⋆. Seyfert 2 galaxies are shown as red diamonds, and the control sample is represented by gray circles (DustPedia) and green squares (5MUSES). For purely illustrative purposes, the best-fit trend (dashed black line) for the control sample of inactive galaxies is shown, and the two dotted black lines are the same trend shifted by a factor of 0.5 dex in either direction. The best-fit slope (α) and normalization (β) are reported in each panel. Right panels: same scaling relations as in the left panels, but with binned data to underline the average trend of active and inactive galaxies. The red-shaded regions represent the range of values of AGN obtained assuming an α_CO in the range between the Milky Way-like value (α_CO = 4.3 M_⊙ pc⁻² (K km s⁻¹)⁻¹) and α_CO = 1.1 M_⊙ pc⁻² (K km s⁻¹)⁻¹, typically used for the central region of local AGN (see the main text for further details). The bins were chosen to include the same number of sources. The mean value and error bars (standard deviations) in each bin were determined with a bootstrap procedure using 10 000 iterations.