The endowment effect suggests that people become attached to objects that are in their possession, and they demand a higher price to sell an object they own than they would be willing to pay to buy the same object. The results of four experiments support the suggestion that “possession attachment” is related to adult attachment styles in close relationships. Measures of attachment style in close relationships significantly predicted both actual and hypothetical selling prices moderating the endowment effect (Study 1), and significantly correlate with ratings of possession attachment (Study 2). Specifically, attachment anxiety is positively correlated with the selling prices of objects, while attachment avoidance shows no significant relation with object evaluation. The third and fourth experimental studies further demonstrated that attachment anxiety enhances possession evaluation and inhibits trades. The studies used real commodities and real money, and therefore, they have implications for everyday decisions as well as for the development of theories to better understand decisions about trades, negotiations, and choice of goods. Copyright © 2010 John Wiley & Sons, Ltd.