Background: In recent years many studies have shown that the use of cochlear implants (CIs) improves children's skills in processing the auditory signal and, consequently, the development of both language comprehension and production. Nevertheless, many authors have also reported that the development of language skills in children with CIs is variable and influenced by individual factors (e.g., age at CI activation) and contextual aspects (e.g., maternal linguistic input). Aims: To assess the characteristics of the spontaneous language production of Italian children with CIs, their mothers' input and the relationship between the two during shared book reading and semi-structured play. Methods & Procedures: Twenty preschool children with CIs and 40 typically developing children, 20 matched for chronological age (CATD group) and 20 matched for hearing age (HATD group), were observed during shared book reading and semi-structured play with their mothers. Samples of spontaneous language were transcribed and analysed for each participant. The numbers of types, tokens, mean length of utterance (MLU) and grammatical categories were considered, and the familiarity of each mother's word was calculated. Outcomes & Results: The children with CIs produced shorter utterances than the children in the CATD group. Their mothers produced language with lower levels of lexical variability and grammatical complexity, and higher proportions of verbs with higher familiarity than did the mothers in the other groups during shared book reading. The children's language was more strongly related to that of their mothers in the CI group than in the other groups, and it was associated with the age at CI activation. Conclusions & Implications: The findings suggest that the language of children with CIs is related both to their mothers' input and to age at CI activation. They might prompt suggestions for intervention programs focused on shared-book reading.