The effect of lattice defects and microstructures on hydrogen distribution in pure aluminium, Al-4 mass% Cu and Al-1 mass% Mg2Si alloys has been studied by tritium electron microautoradiography. It was found that in pure aluminium and both the alloys, dis[ocations and grain boundaries act as short-circuiting diffusion paths and also as trapping sites for hydrogen, it was found that the Guinier-Preston (GP) zones in the Al-1 mass% Mg2Si alloy do not act as trapping sites but as repellants for hydrogen, in contrast to the GP zones in the Al-4 mass% Cu alloy in which they act as trapping sites for hydrogen. In the Al-1 mass% Mg2Si alloy, the interfaces between the matrix lattice and the metastable beta’ precipitate and between the matrix lattice and the equilibrium beta precipitate, were proved to be strong trapping sites for hydrogen. In the Al-4 mass% Cu alloy, the equilibrium theta precipitate itself has been found to be able to trap hydrogen.