INTRODUCTION: The short forms of MacArthur-Bates Communicative Development Inventories (MB-CDI) are widely used for assessing communicative and linguistic development in infants and toddlers. Italian norms for the Words and Gestures (WG) and Words and Sentences (WS) short forms overlap between 18 and 24 months. OBJECTIVE: To evaluate the agreement between these two forms. METHODS: Parents of 104 children aged 18-24 months filled in both questionnaires. RESULTS: The two questionnaires showed high agreement in measuring expressive vocabulary size and the percentile of lexical production and good agreement in identifying children at-risk for language delay (75% of the cases were accurately identified). Both short forms include a list of 100 words and a set of questions investigating potential risk factors for communication and language disorders. Ten children with an expressive vocabulary <10th percentile were compared to 10 with typical language development. Scores for children <10th percentile were significantly lower than their peers, in addition to scores of lexical comprehension, gesture-word, and 2-word combinations, and phonological accuracy, imitation of new words, and decontextualized use of language. CONCLUSIONS: Short forms of the Italian MB-CDI can be used interchangeably for evaluating lexical production, but each one offers different quantitative and qualitative information on the behaviours related to language acquisition.