The diffusion problem of light gases in the atmosphere of Titan is reassessed after Voyager encounter. An analytical solution of the diffusion equation for a spherical geometry and an isothermal atmosphere provides a vertical profile of molecular hydrogen when physical parameters measured during Voyager encounter with Titan's atmosphere are used. The H//2 concentration varies from 5. 5 multiplied by 10**7 cm** minus **3 at a turbopause radial distance of 3500 km to 3. 1 multiplied by 10**5 cm** minus **3 at a critical level of 4100 km radial distance where the escape flux is 2. 5 multiplied by 10**9 cm** minus **2 s** minus **1. The importance of the escape flux is such that a variation of plus or minus 200 km of the turbopause level does not change the concentration at the critical level by more than 10%. The observed existence of an atomic hydrogen torus leads to an estimation of the concentration of a molecular hydrogen torus that has not yet been detected. The estimated concentration of H//2 in the torus is 100 cm** minus **3.