Annulment and declaration of nullity of marriage are legal institutions in two separate legal orders but based on similar premises. The purpose of both processes is to show whether a given marriage was validly concluded. As regards similarities, analogy can be shown in the grounds for an application for marriage annulment or an application for a declaration of marriage nullity, locus standi, time limit for bringing an action (or libellus), and regarding the consequences of a judgment annulling a marriage or declaring nullity of a marriage. As regards the first two categories of criteria for the initiation of a process, the following should be specified: marital impediments and defects in the declaration of will. With respect to the former, the church legislator provides for a broader catalogue of impediments, just like in the case of defective declarations of will. The third category specifies different conditions for two processes. Under civil law, this would be defective power of attorney, while under canon law – the lack of the canonical form. However, it should be pointed out that despite these discrepancies, the content of these criteria is in many respects analogous, yet differently systematised by the legislator. The precise determination of differences is important since it helps to systematize the acquired knowledge and precisely point out the characteristics of two separate processes, which are mistakenly regarded as identical.