The influence of mycorrhiza with Hebeloma crustuliniforme on plant growth, leaf water potential, leaf gas exchange and chlorophyll content in 3 poplar varieties (P. petrowskyana, P. deltoides cv. Plantierens, P. balsamifera) were investigated. After 11 weeks of plant growth mycorrhizal structures (frequency of mycorrhiza - FF%, intensity of the mycorrhizal colonization - MC% were observed in plant roots belonging to the treatment (M). No statistically significant differences were observed in the frequency of mycorrhiza (F%) and intensity of the mycorrhizal colonization (MC%) in plant roots of the treatment M between the examined poplar cultivars. The frequency of mycorrhiza (FF%) was high, and it reached about 75%, while the intensity of the mycorrhizal colonization (MC%) by fungi hyphae was slightly lower and equaled to from 49 to 58%. For plants, exposed to the inoculation with mycorrhizal fungi, advantageous and statistically significant changes in the measured physiological traits were observed. In this research advantageous differences in reactions between inoculated and non-inoculated poplar cultivars were observed, which was shown in the measurements of some physiological traits. Compared to the control plants (C), in the case of plants of the treatment (M) greater increase in plant height (∆Н), increase in chlorophyll content (SPAD), higher values of water potential (Ψ), and increase - in photosynthesis rate (Pn), stomatal conductance (gs) and water use efficiency (WUE), and decrease in transpiration rate (E), were observed. Although those differences were relatively small, we may presume that if they occur through a longer period they may become more distinct e.g. as a greater increase in height in the inoculated plants.