The laser diffraction method (LDM) is a relatively new technique that is increasingly
used in measurements of the particle size distribution (PSD) of soil and sediments.
It has significant advantages (high precision, simple and rapid measurement) but the
PSDs obtained by LDM often differ from those obtained with previously used sieve-sedimentation
methods (SSMs). The main factors influencing the measurements that use LDM (among
others: soil pretreatment, construction of the device settings of the operator, specificity
of soil material, and the problem of fulfilling the assumptions of the method) are
presented and the problem of comparability with SSM. New areas of investigations using
LDM are also discussed. The work concludes with a set of postulates that should be
taken into account to standardize LDM and increase the comparability of results, not
only with SSMs but also with the PSDs obtained in other laboratories, including the
diffractometers deriving from other producers.