The ability of the active microwave remote sensing to complement existing optical vegetation indices has been explored by variety of studies. To demonstrate these complementarities, we investigate synergies between the slope parameter from the ERS scatterometer (ERS-SCAT) and the Normalized Difference Vegetation Index (NDVI). While the NDVI is strongly linked to the absorption of photosynthetically active radiation (PAR), the active microwave signal has the ability to penetrate partially a vegetation canopy, bouncing back from its stalks and stems and so returning a signal (i.e. backscatter) that is influenced by the canopy structure. While this interaction is rather complicated and not fully understood, this study suggests the ability of the ERS-SCAT slope parameter to differentiate between varieties of structural vegetation properties and complement so to existing optical vegetation indices.