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Due to a high market demand, apple cultivation in Albania is spreading outside its typical and optimal cultivation area, towards the warm, semi-arid coastal areas, benefiting from the advantages of earliness and closeness to the main markets. Planting of several cultivars in the same orchard requires accurate tuning of the irrigation regime based on water use efficiency (WUE) principles. The object of this study was to assess the behaviour of these cultivars under a cultivation regime with high radiation and temperatures for a more accurate determination of irrigation needs in the orchard. The study was conducted in the area of Lushnja during 2011 in a commercial orchard of 2.5 ha, trained as central and being in its 6th year. Measurements included flow based at both branch and trunk level as well as trunk diameter variation (TDV) using dendrometers placed at the trunk and at the central leader. Gypsum block sensors were used to measure soil water potential at different depths while a portable meteorological station measured global radiation, temperature and relative humidity. Potential evapotranspiration (PET) and vapour pressure deficit (VPD) were calculated using a model implemented in Mini32 software. Trees were subjected to a gradually increasing water stress. Biometric measurements of canopy elements like vegetative versus reproductive shoot ratio, branch diameter and length, rootstock and trunk diameter, affinity index were also measured and analysed. Maximum values of PET varied between 0,8-0,9 mm/h during the entire measurement period. Sap flow (SF) values changed significantly between cultivars and were strongly correlated with global radiation and VPD. The trunk sensor values integrated well the transpiration of the entire tree and were correlated with the values of shoots. Due to their vigorous growth, the cultivars Red Delicious and to some degree also Golden Delicious showed higher levels of transpiration. The comparison of SF values under low and high SWP showed that Pink Lady on M9 is more sensitive to soil water availability.