Abstract: A method for preparing an advanced epoxy cationic resin from an opoxy-based resin containing oxirane groups by converting at least some of the oxirane groups to cationic groups, wherein the improvement is using as the epoxy-based resin an advanced epoxy resin obtained by reacting in the presence of a suitable catalyst (1) a diglycidylether of an aliphatic diol which is essentially free of ether oxygen atoms, such as a diglycidyl ether of 1,4-butanediol, (2) a diglycidylether of a dihydric phenol, for example a diglycidyl ether of bisphenol A and (3) a dihydric phenol such as bisphenol A and optionally a capping agent such as p-nonylphenol.Coating compositions suitable for electro-deposition are prepared from the product obtained by the process.