Displacement ventilation (DV) systems were initially developed as an efficient buoyant pollutant removal strategy for Scandinavian industrial halls in the 1970's. In the following decades these systems started to be used in mechanical cooling of office buildings and auditoriums. Designing displacement ventilation systems is more challenging than conventional overhead mixing systems. Most DV system designs require simplified modeling tools. Existing simplified models of DV were validated using air temperature measurements performed in test cells that cannot reproduce the conditions that exist in large rooms with thermally active boundary conditions. There is a lack of measurements that investigate the performance of DV systems in occupied large rooms. With the goal of reducing this knowledge gap, this paper presents a set of detailed temperature and CO2 measurements in two occupied large rooms with recently designed DV systems. The measurements were performed.in two recently refurbished rooms located in Lisbon: a large Concert hall and an adjacent Orchestra rehearsal room. The measurements and subsequent analysis were used to assess the actual performance of large room, state of the art, DV systems. In addition, these measurements were used to determine the modeling error of the three-node DV model implemented in EnergyPlus when simulating large rooms. Comparison between simulations and measurements revealed a good agreement: the average simulation error obtained by averaging the error of all measurements in all temperature nodes is 5.9%, with the largest deviation occurring in the floor level node (7.1% approximate to 0.4 degrees C) average simulation error of 5.9% (the average of error of all measurements in all nodes). (C) 2017 Elsevier Ltd. All rights reserved.