Environmental factors that influence stomatal conductance (g s ) interact through a complex network of signal transduction and have therefore highly interdependent effect.In the present study we examined how plant water status affects stomatal sensitivity to the change of CO 2 concentration ([CO 2 ]). We investigated the short-term dynamic of stomatal response to a sudden [CO 2 ] increase (from 400 to 700 µmol(CO 2 ) mol -1 ) in maize supplied with different amounts of water (resulting ψ w = -0.35, -0.52 and -0.75 MPa). Gas exchange measurements were performed in short logging intervals and the response was monitored under two different levels of water vapour pressure deficit (VPD) of 1 and 2 kPa in order to observe the impact of air humidity. Generalized logistic curves were fitted to standardized stomatal response data, which enabled us to objectively estimate the level (relative decrease of g s ) and the dynamics of the response.Soil water stress and high VPD significantly decreased relative stomatal closure in response to [CO 2 ] rise, but simultaneously accelerated stomatal response to [CO 2 ], as revealed by shorter half life (t 1/2 ). VPD significantly affected the response of well-watered plants. In contrast, a fast stomatal reaction of water-deprived plants was predetermined by a low xylem water potential (ψ w ) of the leaf and the influence of air humidity was minor.