Human paraoxonase 1 (hPON-1) is a protein that has been studied in relation to its antioxidant and anti-atherosclerotic properties. Despite extensive studies, the molecular mechanisms responsible for its functional properties remain unclear. During the last decade, a new partner of hPON-1 has been identified. Hidden for a long time because of a similar molecular weight with hPON-1, this protein, termed human phosphate-binding protein (HPBP), may contribute to the biological functions of hPON-1. Belonging to the DING protein, a sub-family of phosphate binding proteins (PBP or pstS), HPBP stabilizes hPON-1 and might prevent calcification of arteries in case of advance atherosclerosis. The role of other DING proteins in some calcification processes (i.e. nephrolithiasis) and the identification of HPBP in the atheroma plaque support this hypothesis. Nevertheless, the relevance of hPON-1/HPBP as well as the molecular determinants in atherosclerosis remains to be elucidated.