The article presents three issues concerning practical problems at the junction of an ordinary appeal, an appeal in simplified proceedings and a cassation complaint, as well as proposals of solutions to those problems based on the case law of the Supreme Court. The first problem concerns the issue of whether the cataloguing of grounds of appeal in simplified proceedings is an element that distinguishes the model of simplified appeal from the model of full (ordinary) appeal. In solving the above problem, two resolutions of 7 Supreme Court judges have been indicated (of 31 January 2008, III CZP 49/07 and of 23 March 1999, III CZP 59/98) and ambiguities contained in their justifications have been explained. A solution has been proposed that the cataloguing of grounds for a simplified appeal does not constitute an element distinguishing this appeal from an ordinary appeal, since regardless of the way in which the allegations have been formulated by the appellant, each allegation may be qualified either as a violation of procedural law or substantive law. The second issue is related to the problem of how to correctly qualify the court’s failures:
to a violation of procedural law, the consequence of which is an erroneous establishment of the facts, or to a violation of substantive law? The article cites Supreme Court case law to help distinguish which failures of the court belong to the sphere of facts and which to the category of legal assessments. The third issue is whether it is permissible for the Supreme Court to set aside a judgment
under appeal on the grounds of insufficient or incorrect findings of fact by means of an allegation of an infringement of substantive law. The article cites and comments on the Supreme Court’s case law allowing for the possibility of issuing a cassation judgment in
a situation where the court of second instance applied the substantive law (defective subsumption) to the insufficiently established state of facts by the court of second instance.