The purpose of this study is to explore quality dimensions in the service that B2B e-marketplaces provide to their users in the construction sector. The study identified four key B2B service quality dimension as perceived by online selling side users of e-marketplace: reliability and privacy, utility of the information, value-added services, and efficiency. The basis of the study is an analysis of empirical data provided by 197 Spanish e-marketplace users. All the variables extracted had a significant positive impact on the outcome variable –client loyalty– with reliability and privacy being those of the greatest influence. To improve the services provided to users and ensure their future loyalty, it would be interesting for managers to be aware of these dimensions and to invest in improving these aspects for the future.