Sketch of the line emitting region in a ProDiMo disk model. The cumulative line flux as function of radius is shown in the lower part, and the cumulative line intensity at some given radius, as function of height, is sketched in the insert on the top left. We consider the region between R_0.15 and R_0.85 and between z_0.15(r) and z_0.85(r) as the line emitting region, where the respective cumulative quantities reach 15 and 85%, respectively, Σ_0.15 and Σ_0.85 are the column densities at R_0.15 and R_0.85 respectively.