Soil erosion is a serious problem especially on arable land in the loess areas of southern Poland. Reliable data of soil erosion are important to propose a proper method of soil conservation. Measurements of ¹³⁷Cs inventory allow obtaining both long-term mean value of soil erosion and spatial pattern of soil erosion. To obtain quantitative results of soil erosion from ¹³⁷Cs measurements one of the mathematical models must be used. Currently, there are many such models in circulation and the results of calculations of soil erosion depend not only on the particular model but also on values assumed for parameters of this model. This paper describes some problems related to calculating soil erosion and deposition based on ¹³⁷Cs data, namely, the influence of additional parameters on calculated soil erosion is considered. In particular, we have considered the influence of values assumed for plough depth, γ factor, particle size correction factor, soil density and the contribution of the post-Chernobyl deposition to the total caesium deposition on the calculated soil erosion values. The calculations of soil erosion have been done for four, most commonly used models, using real caesium inventory data collected by the authors. The influence of errors of model parameters on the results of soil erosion rate estimates is about 1%, or less for 1% relative error in the parameter.