Imajući u vidu protivrečnosti između starih nalaza o ranoj usvojenosti padežnog sistema (dobijenih iz uzoraka spontanog govora) i novijih nalaza o relativno kasnom oslanjanju na padežni sistem u procesu razumevanja rečenice (eksperimentalna istraživanja), cilj ovog rada je bio razjašnjavanje stepena razumevanja imeničke morfologije kod dece na predškolskom uzrastu. U nizu eksperimenata ispitivano je razumevanje rečenica koje sadrže imenice u padežnim oblicima, kao i određene predloško-padežne kombinacije. Zadatak ispitanika je bio da pomoću modela demonstriraju značenje date rečenice. Rezultati su pokazali da se proces odvija tokom celog predškolskog perioda. Stepen razumevanja različitih predloga se diferencira po uzrastu, ali njihovo prisustvo je u rečenici značajno jer predstavljaju jedan od sigurnih indikatora sintaksičke distribucije. Sam morfološki oblik imenice nije značajna determinanta razumevanja. Ali, ako promena oblika imenice podrazumeva i promenu sintaksičke funkcije ili specifičnog značenja, tada dolazi do različitog stepena razumevanja zavisno od samog značenja, tj. date relacije koju nosi.In some previous longitudinal studies of spontaneous speech in Serbian (Mikeš & Vlahović, 1966; etc.) it was found that children acquire the inflectional case system very early, and that this process is completed by the age of three years. On the other hand, Mimica (1986, 1987) found that in the sentence comprehension task children start to use the case strategy only at the age of six. Before they acquire the inflectional case system as a syntactic role indicator, they used supplementary word order, semantic, and pragmatic strategies to interpret transitive sentences. In the present research the comprehension of prepositional noun phrases in Serbian by children 3 to 7 years old was studied. Case inflections, prepositions and word order were varied in a series of experiments using the sentence interpretation task. Children were asked to demonstrate the meaning of sentences containing prepositions and marked cases by means of models and toys given to them. The results of the present study indicated: a) comprehension of different prepositions is acquired all through the preschool period, b) the presence of a preposition facilitates the comprehension of subject - object syntactic roles, with significance of word order strategy being lost, c) comprehension of sentences containing prepositions is based primarily on the comprehension of the prepositions, while the contribution of inflectional suffixes is marginal, and significant only if they change the sentence meaning