Creditor protection is the main goal of insolvency proceedings. In order to accomplish said goal, various legal institutes are created to prevent damage to creditors during insolvency. One of the particularly important issues is how to prevent related parties from using their specific insider status and obtaining gain for themselves, harming the other creditors. The emphasis in this paper is on shareholders that provide additional funding to the financially distressed company. The main issue is how to treat said transaction in insolvency - as a loan or as an equity contribution, which has consequences, mainly on their priority order in insolvency. The paper is thematically divided into two parts. The first deals with issues related to subordination as a legal institute, while the second puts this issue in the context of selected individual legal systems. The author identifies two groups of legal orders - ones that don't regulate this issue and the ones where the subordination has its legal foundation. Comparative overview covers on the one hand systems that have subordination based on objective criteria, such as German legal system that has rich history in application of this legal institute, Austrian and Spanish legal systems that have used German law as a role model, and on the other hand the US law that is an example of opposite approach based on subjective criteria (equitable subordination).