Nowadays, organizations estab lish Business-to-Business (B2B) collaborations with their business partne rs. Inter-organizational collaboration is carried out through the execution of collaborative business processes. Organizations are requiring and under going the setting up of dynamic B2B collaborations, instead of conducting fa ce-to-face negotiations and agreements for executing collaborative processes. Th is implies that business partners, maybe without a previous relationship, agree dynamically on the execution of collaborative processes based on predefined models of these processes. In this work, we propose an B2B collaboration platform which provides agent-based systems and interaction mechanisms in order to enable organizations to establish dynamic agreements with their partners and carry out the decentralized execution of collaborative processes. Agents use models of collaborative processes to enact them in a dynamic way. The role an organization performs in a collaborative process is translated into a Petri Net model that a collaboration agent interpret to execute the process.