The paper reports on an experiment designed to investigate the interpretation and misinterpretation of Polish sentences such as Gdy Jan pisał list spadł z biurka (e.g. “While John was writing the letter fell off a desk”), paralleling English garden path sentences such as While John hunted the deer ran into the woods. The locally ambiguous NP-V-NP region in sentences of this sort may result in the key noun phrase being incorrectly interpreted as the object in the fronted temporal clause. The experiment was conducted using E-Prime software and involved comparing the participants’ comprehension of garden path sentences in three different conditions with their comprehension of equivalent non-garden path sentences. This was achieved by examining the participants’ performance on comprehension questions probing the interpretation of the subordinate clauses, establishing the times they needed to answer the questions and checking the level of their confidence in their responses. The goals of the experiment were to establish whether the Polish sentences in question force the comprehender to form erroneous interpretations which persist in his mind and to determine to what extent the persistence of the initial incorrect interpretation is influenced by the morphosyntactic properties peculiar to Polish. The results of the experiment indicate that though the Polish sentences under investigation do not trigger a particularly strong garden path effect, the information carried by the case endings and the thematic roles nouns are likely to have in specific contexts affect the way locally ambiguous sentences are analysed.