This work investigates the thermal performance of buildings in Cyprus and application of a particular passive technology; Phase Change Materials (PCMs) for the ultimate aim of reducing indoor air temperatures and energy supplied for the cooling season.PCMs for passive building applications are emerging technology and have not been tested for the buildings of Cyprus neither by computer simulations nor by practical applications. In this work, particular PCM end product; wallboard, having phase change temperature of 26 oC is employed together with various construction materials and simulated for buildings of Cyprus. Description of the current state in Cyprus has been carried out in terms of low energy building studies, widely used building fabric and building statistics. There is a huge gap in Cyprus in the field of energy performance and thermal comfort of buildings, which creates big room for research. Climatic design of buildings has been abandoned resulting in poor thermal comfort and increased energy consumption. There is still no regulation in place regarding the thermal performance of buildings in North Cyprus.Recent weather data of different Cyprus locations has been investigated and compared with the simulation weather data files that are employed in this work. The author has demonstrated that Finkelstein-Schafer statistics between recent weather data of Cyprus and simulation weather data files are close enough to obtain accurate results.Dynamic thermal simulations has been carried out by using Energy Plus, which is a strong and validated thermal simulation program that can model PCMs. Simulations are done for two different building geometry; "simple building" and "typical building" by employing different construction materials. Simple building is a small size box shaped building and typical building is a real existing building and selected by investigation of the building statistics.Simulation results showed that with this particular PCM product, indoor air temperatures and cooling energies supplied to simple building is reduced up to 1.2 oC and 18.64 % when heavier construction materials are used and up to 1.6 oC and 44.12 % when lighter construction materials are used. These values for typical building are found to be 0.7 oC, 3.24 % when heavier construction materials are used and 1.2 oC, 3.64 % when lighter construction materials are used. It is also found that, if thinner walls and slabs are used in the buildings the effectiveness of the PCM lining increases in significant amount.