Collision cross-sectional parameters such as collision diameters, sigma(AB), and maximum attractive energies, epsilon(AB), between two molecules A and 13, were obtained from experimentally measured gas diffusion coefficients. The diffusion coefficients at infinite dilution were measured at different temperatures (315.2-449.8 K), by a gas chromatographic method called reverse-flow gas chromatography (RF-GC), for the following systems: CO-H-2, CO-He, CO2-H-2, CO2-He, C2H4-N-2 and C2H6-N-2. The obtained diffusion coefficients and cross-sectional parameters, are compared with literature values, which have been determined by other experimental and theoretical methods. The most interesting finding is the large deviation of the directly determined cross interactions of the present work, from those obtained by using simple combining Lorentz-Berthelot (LB) rules and/or other than diffusion transport properties of molecules. (C) 2004 Elsevier B.V. All rights reserved.