The effect of compression force, compression speed and the amount of granulation liquid on the porosity parameters determined from lactose, glucose and mannitol tablets by high-pressure mercury porosimetry was investigated. Compression force affected all parameters measured, except the total pore surface area of lactose tablets. The changes in tablet microstructure with increasing compression force were particularly well detected from the pore volume size distributions of tablets. Compression speed affected the total pore volume of lactose tablets, both mean and median pore diameters of lactose tablets and mannitol tablets compressed from granules produced with a low amount of liquid, and the median pore diameter of glucose tablets. The compression speed dependence of these parameters was a sign of the time-dependent deformation of materials during compression. The amount of granulation liquid affected the total pore surface area of lactose and mannitol tablets. With a high amount of liquid, the surface area of pores was greater. The mean pore size of all tablets and the median pore diameter of mannitol tablets were smaller when a high amount of granulation liquid was used. Even when compressed with a high force, the pore volume size distributions of mannitol tablets with a low amount of granulation liquid were broader and the maxima were at larger pore diameters. It was concluded that each porosity parameter measured characterised the pore structure of compressed tablets from a different aspect. Thus, the use of all porosity parameters proved to be useful.