A promissory note and the so-called promissory note declaration (promissory note agreement) are key institutions in contemporary transactions concerning promissory notes, with most notes issued as incomplete (blank) ones. A number of decisions of higher courts have been devoted to the interpretation of both types of declarations of intent, but they often simplify matters and do not dispel all existing doubts. It is therefore necessary to systematize this knowledge, which must lead to a twofold conclusion. The combined method of interpretation of declarations of intent based on the wording of Article 65(2) of the Civil Code is fully applicable to promissory note declarations. Meanwhile, with regard to the contents of a promissory note, interpretation must - in principle - be based on the objective method of interpretation. However, this rule allows for certain exceptions.