AbstractThe water fluxes and the CO2exchange of three leaf succulents,Othonna opima, Cotyledon orbiculataandSenecio medley‐woodii, with different leaf anatomy, growth form and CO2fixation pathways (C3, CAM) were monitored with a gas exchange cuvette which was combined with a potometric system to quantify water uptake. Measurements, which are primarily valid for plants with a sufficient water supply, were made during 6 to 10 consecutive days under constant experimental conditions. Water uptake for 24 h exceeded water loss by transpiration only for aS, medley‐woodiiplant with 10 expanding but only 7 mature leaves. In this case the gained water evidently is put into leaf expansion. All other plants showed balanced transpiration and water uptake rates.O. opimaandC. orbiculatahave a similar life form, similar water storage volumes and the same natural habitat but their diurnal water uptake patterns differ significantly. In the C3plantO. opimawater uptake increased when the transpiration increased or transpiration rates were higher than uptake rates and vice versa. On the contrary the CAM plantC. orbiculatatranspired during the dark period at constant or decreasing rates but showed steadily increasing uptake rates.Senecio medley‐woodii‐andC. orbiculataare CAM plants with similar diurnal water uptake patterns with its maximum in uptake during or towards the end of the CO2dark fixation period. Water uptake ofC. orbiculatawas at its minimum at the end of the light period despite transpiration being maximal. The results were discussed considering the different CO2fixation pathways. In the investigated CAM succulents,C. orbiculataandS. medley‐woodii, the CAM influenced water uptake throughout the whole day and not only during the CO2dark fixati