This paper deals with the acquisition of diminutives by four Italian children with three objectives: to highlight parallelisms and differences in input and output data; to contrast the mechanism of item-based learning (cf. Tomasello 2003) to the dual-route model (Clahsen et al. 2003) as regards the acquisition of diminutives; to investigate whether the productive use of diminutives is a simplifying strategy for acquiring the morphology of non-productive, opaque inflectional classes. The analysis of data reveals a common developmental pattern in the children and that the acquisition of diminutive suffixes (especially -ino) can be ascribed to children’s rule extraction. The children, more markedly two of them, use the regular inflection of the diminutives as a strategy to simplify the input data.