The common features of spectral reflectance from vegetation foliage upon leaf dehydration are decreasing water absorption troughs in the near-infrared (NIR) and short-wave-infrared (SWIR). We studied which leaf water index in the NIR and SWIR is most suitable for the assessment of leaf water content and the detection of leaf dehydration from the laboratory standpoint. We also examined the influence of the thickness of leaves upon leaf water indices. All leaf water content indices examined exhibited basic correlations with the relative water content (RWC) of leaves, while the R 1300 /R 1450 leaf water index also demonstrated a high signal strength and low variability (R 2 >0.94). All examined leaf reflectance ratios could also be correlated with leaf thickness. The thickness of leaves, however, was not independent of leaf RWC but appeared to decrease substantially as a result of leaf dehydration.