[en] Our first countrywide study carried out in 1991-1993 determined both geographical and depth distributions of the deposited 1^34Cs and 1^37Cs in the Estonian soil. According to the results of this study and an independent air-borne scanning, radiocaesium originating from the 1986 Chernobyl accident with the mean deposition of 2 kBq m^-2 was extremely unevenly distributed over the country . The mapped distribution is presented in Fig. 1. Our estimates demonstrated that about 2/3 of the total 1^37Cs inventory in Estonia was deposited in Ida-Virumaa County, NE Estonia, where the maximum depositions reached 40 kBq m^-2. The region was revisited for soil sampling in 1998-2001. Undisturbed soil profiles down to a depth of ∼ 20 cm were collected and the 2-3 cm sample core slices analyzed using a low-background HPGe gamma spectrometer (42% efficiency and 1.7 keV resolution). As in the previous study, both total depositions and depth distributions of the deposited 1^34Cs (where possible) and 1^37Cs activity concentrations were determined. Depth distributions of the deposited activity showed considerable site-specific variations. In addition, it appeared that in comparison with our previous study, clear features of time-dependent migration to deeper soil layers were evident. The preliminary modeling has demonstrated that a lognormal distribution with varying parameters fits satisfactorily the determined depth-distributions of the Chernobyl radiocaesium activity concentration. An attempt was made to apply a single model to describe the observed time-dependent depth-distribution pattern over the time period of 1986-2001. We started from the multi-compartmental migration model for undisturbed soil (here Model RP72), presented in Fig. 2. This model has been elaborated basing on experimental migration results for Pu for a time period up to 30 y. For our application, the model is modified to account for the radioactive decay of 1^37Cs. The results of modeling using the original transfer parameters are given in Fig. 3 (a)