At present we can observe the increasing role of cooperation among companies all around the world. Cooperation includes many forms, such as alliances, joint ventures, networks, clusters, outsourcing and others. Trust is one of the most important factors of success of any cooperation activity, because it can lower transaction costs, increase productivity and innovativeness, facilitate inter-organizational relationships and resolve conflicts. Therefore the paper discusses the basic problems of trust in alliance networks. The text consists of theoretical deliberations devoted to alliance networks and trust. The practical case of the company from machine industry that formed a portfolio of alliances based on trust is also an important part of the text. The conclusion of the paper is that portfolio of alliances based on trust is worth pursuing.