We present and discuss results obtained by the model describing distribution of a polymeric modifying agent along wood fibers of a small-dimensional crosscut end under the condition of isothermal diffusive impregnation of solutions of low-molecular co-polymers. We obtain an analytic model combining a solution of differential equation governing the one-dimensional mass transfer and experimental data on effective coefficients of mass transfer. The model is adequate to a particular case of modification of small-dimensional crosscut end of wood. It can be used for optimization of technologic processes and technologic forecasting.