The gas-phase structures and energetics of protonated glycine with one to three water molecules was investigated using ab initio molecular orbital and density functional theory. It is well established that amino acids have zwitterionic structures in aqueous solution, where the amino group is protonated and the carboxyl group loses a proton. The general assumption that zwitterions do not exist in the gas phase has been the subject of much debate from experimental and theoretical approaches. The present work is considered along with previous results obtained experimentally using a high pressure mass spectrometry technique with the objective of proposing valid gas phase structures for this amino acid ion complex.