A theoretical analysis of mass transfer kinetics based on similarity variables method for gas-liquid countercurrent flow has been done. The obtained numerical results for the mass transfer rate (Sherwood number) in case of a laminar boundary layer with flat phase boundary are compared with analogous results for co-current flow. The ratio between the mass transfer velocity and the dissipation energy in boundary layer is determined. The advantages of co-current flow because of lower energy losses than in case of counter-current one are shown.