In this study we investigate the re-introduction of referents in the Frog stories told by Italian children aged 4-10 (N = 100). We found that for every age group full nouns are the most frequent forms used for reference re-introduction. Null forms, such as clitic pronouns or person/number inflection on the verb, are the second most frequent forms. A detailed analysis of null forms shows that children of different ages exploit different properties of the verbal and non-verbal context which can make a referent predictable. Compared to preschoolers, elementary school children are more likely to use null forms when the semantic content of the verb, or the structure of the preceding text make referents inferrable. On the other hand, preschoolers tend to exploit the importance of a character in the story plot, or the visual availability of the referent in the non-verbal context, as properties that make an entity salient enough to prevent the speaker from using overt linguistic forms such as full nouns. Our study confirms results of previous research, showing that elementary school children are more competent than preschoolers in integrating the semantic content of the current utterance into the context generated by previous discourse.