The present study aims at analysing the role of infinitival clauses (INFCs) in German child-adult dialogue. In German subject-less INFCs are a grammatical sentence pattern. Extensive corpora of spontaneous speech between 6 children aged 1;5 to 2;10 and adults were analysed applying structural and contextual analyses. We extended Freudenthal, Pine and Gobet's (2010) model of lexically specific learning to include INFCs in adult input. Results show that frequencies of adult INFC and MOD+INF clauses are related to child INFCs. We interpret these results as reflecting shared verb vocabulary and, regarding INFCs, as an adaptation of adult CDS to child grammatical structure. While most child INFCs have modal meaning, some occur in non-modal contexts. The majority of child INFCs are subject-less clauses with final infinitives and therefore grammatical. Results are discussed in terms of the pragmatic function of child and adult INFCs and the role of adult INFCs in German CDS.