In this paper, performance of solid and perforated Pi-type breakwaters was investigated experimentally. Both regular and irregular waves were used during testing. Four depths of immersions were selected for each breakwater and wave type. Different wave groups were generated over these breakwaters, and the transmission, reflection and energy-dissipation characteristics were determined. The results of the experimental study were evaluated and some empirical expressions based on the results were suggested to define the transmission, reflection and energy-dissipation coefficients for different immersion depths of solid and perforated breakwaters under regular and irregular waves. Moreover, performance of solid and perforated Pi-type breakwaters were compared with that of solid and perforated U-type breakwaters investigated by Gunaydin and Kabdasli [2006. Performance of solid and perforated U-type breakwaters under regular and irregular waves. Ocean Engineering 31, 1377-1405]. These comparisons showed that the most reasonable model and wave type are selected to determine requiring performance parameters. (c) 2006 Elsevier Ltd. All rights reserved.