Lead di-acetate tri-hydrate (Pb(CH3COO)2.3H2O undergoes a second order structural phase transition around 100K. The organic molecules in this structure form sheets of H bonded molecules. We propose to study the low temperature structure of (Pb(CH3COO)2.3H2O. In this stucture the disorder in the water molecules will most likely disappear. We also propose to study the inflence of partial and full deuteration on the hydrogen/deuteruim network of (Pb(CH3COO)2.3H2O. The crystal structures data will be used in DFT calculations in order to get insight into the ordering process of the H/D bond network.