Mercury porosimetry and nitrogen adsorption methods were used in pore structure and pore surface area characterisation of microcrystalline cellulose powder, granules and tablets. The effect of compression on pore structure and surface area of tablets compressed with three different compression pressures of powder and granules was determined. Densification of MCC in wet granulation led to decreased compactibility in tableting. Effects of granulation on the microstructure of microcrystalline cellulose and plastic deformation of powder during compression were detected with nitrogen adsorption, at the diameter range 3-200 nm. Structure of granules was destroyed during tableting when compression pressures of 196 MPa were used. Fragmentation and deformation of granules were observed from the results determined using both methods. Due to different measurement ranges, different theoretical basis of the methods and behaviour of the samples during analysis, results obtained with mercury porosimetry and nitrogen adsorption methods are not strictly comparable. Results obtained with mercury porosimetry give information on the behaviour of powder and granule particles in granulation or compression, whereas nitrogen adsorption brings out the changes in intraparticular structure of particles. The results obtained using these methods together can be used in the characterisation of behaviour of materials in granulation and tableting.