The intensity and the frequency of extreme drought are increasing worldwide. An elevated atmospheric CO₂ concentration could counterbalance the negative impacts of water shortage; however, wheat genotypes show high variability in terms of CO₂ reactions. The development of the root system is a key parameter of abiotic stress resistance. In our study, biomass and grain production, as well as the root growth of three winter-wheat varieties were examined under optimum watering and simulated drought stress in a combination with ambient and elevated atmospheric CO₂ concentrations. The root growth was monitored by a CI-600 in situ root imager and the photos were analyzed by RootSnap software. As a result of the water shortage, the yield-related parameters decreased, but the most substantial yield reduction was first detected in Mv Karizma. The water shortage influenced the depth of the intensive root development, while under water-limited conditions, the root formation occurred in the deeper soil layers. The most intensive root development was observed until the heading, and the maximum root length was recorded at the beginning of the heading. The period of root development took longer under elevated CO₂ concentration. The elevated CO₂ concentration induced an accelerated root development in almost every soil layer, but generally, the CO₂ fertilization induced in the root length of all genotypes and under each treatment.