I evaluated the use of global remote sensing techniques for estimating plant leaf chlorophyll a + b (Cab; μg cm−2) and water (Cw; mg cm−2) concentrations as well as the ratio of Cw/Cab with the PROSAIL model under possible distributions for leaf and soil spectra, leaf area index (LAI), canopy geometric structure, and leaf size. First, I estimated LAI from the normalized difference vegetation index. I found that, at LAI values <2, Cab, Cw, and Cw/Cab could not be reliably estimated. At LAI values >2, Cab and Cw could be estimated for only restricted ranges of the canopy structure; however, the ratio of Cw/Cab could be reliably estimated for a variety of possible canopy structures with coefficients of determination (R2) ranging from 0.56 to 0.90. The remote estimation of the Cw/Cab ratio from satellites offers information on plant condition at a global scale.