The aim of this study is to analyze Italian Sign Language (LIS) linguistic skills in two groups of deaf signing children at different ages, and to compare their skills with those of a group of deaf signing adults. For this purpose, we developed a new Sentence Reproduction Task (SRT) for Italian Sign Language (LIS-SRT), which we administered to 33 participants. Participants' scores and type of errors were analyzed to investigate similarities and differences related to both chronological age and age of LIS acquisition. Results showed that signs tended to be omitted more frequently by the younger children than both the older children and adults and that non-manual components produced simultaneously with manual components appear to be the most difficult linguistic elements to be acquired and mastered. Our results are compared to those of previous studies using SRTs for other signed languages.