Dependence of CO luminosity concentrations (C_CO) and molecular gas concentrations (C_mol) on the strengths of disk structure (2 + log s_disk). The left two panels show the results for the parent sample, whereas the right two panels show the results for galaxies with i ≤ 65°. The formulas indicate linear fits considering both barred and unbarred galaxies. They are derived using PCA and marked with solid lines. The Pearson correlation coefficients, ρ, for unbarred and barred galaxies are given at the top of each panel.