Comparison between theoretical predictions and observations for surface lithium abundance in the selected binary systems. Lithium evolutionary tracks for low-convection efficiency (α_PMS = 1.0) corresponding to the primary (blue-solid line) and the secondary star (red-dashed line) have been computed for the labelled chemical composition and mass. Shaded area represents the uncertainty regions for the primary (dark-shaded area) and secondary stars in the system (light-shaded area). We also show the primary and secondary evolutionary tracks computed with α_PMS = α_MS (green-solid and black-dashed lines, respectively).