[en] The square-well (SW) model in the semi-analytical modification of the mean spherical approximation (MSA) is used for calculating the self-diffusion coefficients of liquid sodium and potassium in the linear trajectory approximation. The results obtained are found to be in reasonable agreement with the available experimental data and show that a good quantitative description of diffusion properties for liquid metals in the SW-MSA approach can be achieved at the same values of the SW parameters that lead to a good description of their structure characteristics. (author)