Osmotic adjustment is a process that some plants use to maintain both turgor and cell volume as the water deficit intensifies. Few studies have compared differences in water and osmotic potential between leaves and roots in the same plant. Thermocouple psychrometers were used in this work with the objective of identifying differences in water and osmotic potential between roots and leaves of cotton plants (Gossypium hirsutum L., cv. Siokra L-23) during a period of water deficit induced by PEG 6000. Leaves showed a decrease of 0.33MPa (32%) in the osmotic potential. In the roots the same behavior was not observed for this cultivar. The decrease in the osmotic potential of the roots was only 0.03MPa (5.6%).