The comminution process is still governed by a large number of factors that influence the liberation of the valuable components in the ore. A better understanding of these basic factors will provide more certainty about the design of equipment in order to achieve the best liberation and energy efficiency. Impact and bed breakage mechanisms were investigated as two distinctly different modes of breakage. Standard drop weight tests and hydraulic piston-die press tests were conducted with different energy intensities on samples. This paper describes the work carried out for the comparison of mineral liberation and particle size distribution in the particle bed breakage with impact breakage of two different copper ores. Ground products from these two different modes of breakage were screened into size fractions which were analyzed for the particle size distributions by sieve analysis and the degree of liberation by an image analysis system. The results of these analyses were statistically compared to make inferences in relation to the stated objective of the work. Test results indicated that compressive bed breakage mechanism gives finer product particle size distribution and provides better mineral liberation compared to impact breakage mechanism. (C) 2013 Elsevier Ltd. All rights reserved.