The main purpose of this article consists in the demonstration of the performance, in terms of comfort, energy and Indoor Air Quality of a building equipped with an air conditioned system using the radiating ceiling surfaces concept. Radiation based air conditioning systems are traditionally more used in a significant percentage of (both new and refurbished) office buildings in northern and central Europe when compared to Mediterranean climate conditions. The case under analysis refers to an office building with 10000 m2, approx., located near Lisbon, equipped with an air conditioned system based on chilled and chilled/warmed ceiling tiles, complemented with fresh air supply and heat recovery exhaust system. Thermal fluids (chilled and hot water) production is provided by natural gas fired chillers and chillers/heat pumps. Real and simulated building energy consumption are presented and discussed, along with space comfort and IAQ assessments. The objective results obtained for the building under discussion, allows us to conclude that radiation based air conditioning systems are a suitable option under Mediterranean climate, potentially leading to high standard performance, in both energy and internal environment aspects, provided the specific particularities, including thermal envelope quality, are considered and the adequate design criteria are followed.