The statement of claim can contain several claims to the same defendant. However, the plaintiffs make significant mistakes while defining the subject matter of the claim and joining different ways of protecting the violated subjective right. Proving is often exercised inadequately and contradictory, legal reasoning is limited by the common references to the legal norms. The article highlights the problematic issues of arbitration case law practice connected with filing several claims to the same defendant. The authors make recommendations on their resolution and application as well as give examples of correct ways of joining claims. On the contrary, same-name contracts don't create similar interconnected claims. The dispute arising from one contract must be resolved within the framework of one case. The commercial court may single out one or several interconnected claims for consideration in a separate procedure on its own initiative or upon the motion of a party to the case, if it deems separate consideration of the claims complying with the aims of efficient justice. For considering several similar cases jointly with the aims of providing efficient justice and preventing risks of delivery of contradictory judicial acts several similar cases can be joint in a single procedure. As one of the conditions for joining cases the law mentions their similarity, i. e. the claims must be interconnected, due to the grounds of their origin or to the evidence presented. Moreover, one and the same party can be not only the plaintiff on one or several joint claims, but also a defendant on other claims which are to be joined. The case is to be considered from the stage of preparing a case for judicial proceedings.