Abstract: The main aim of the work was to analyse 176 samples taken from the Vah River catchment in Slovakia (from 15-20 cm and 40-45 cm deep) and 190 samples taken from the Nitra River catchment in Slovakia (from 15-20 cm and 40-45 cm deep) using laser analysers ANALYSETTE 22 MicroTec plus from Fritsch and MASTERSIZER 2000 from Malvern. The results obtained by laser diffractometry were compared with pipette method and the regression relationships using linear, exponential, power and polynomial trend were derived. Regressions with the three highest regression coefficients (R2) were further investigated. The result was the percentage of the clay fractions (2nd fraction according to the methodology of the comprehensive soil survey in Slovakia) in soil is the determinant for soil type specification we recommend to use the derived relationships in soil science when the soil texture analysis is done according to laser diffractometry. The regressions with the three highest regression coefficients (R2) were then analyzed in more detail. The highest confidence level R2 was achieved on Analysette MicroTec plus with R2 = 0.53 for Vah catchment and R2 = 0.21 for Nitra catchment and on Mastersizer 2000 it was 0.69 (Váh) and 0.59 (Nitra).