The main topic of this study is the characterisation of primary and secondary fines in a chemical kraft pulp. The former were removed from an unbeaten pulp and the latter from the corresponding decrilled pulp after beating, being their size distributions measured with the Coulter-Multisizer in terms of an equivalent volume diameter. Additionally, some morphological parameters of the fibres were also determined, such as length, width and curl. Handsheets were made with the whole and the decrilled and the unbeaten and the beaten pulps in order to investigate the role of both kinds of fines separately