Children up to school age have been reported to perform poorly when interpreting sentences containing restrictive and additive focus particles by treating sentences with a focus particle in the same way as sentences without it. Careful comparisons between results of previous studies indicate that this phenomenon is less pronounced for restrictive than for additive particles. We argue that this asymmetry is an effect of the presuppositional status of the proposition triggered by the additive particle. We tested this in two experiments with German-learning three- and four-year-olds using a method that made the exploitation of the information provided by the particles highly relevant for completing the task. Three-year-olds already performed remarkably well with sentences both with auch "also" and with nur "only". Thus, children can consider the presuppositional contribution of the additive particle in their sentence interpretation and can exploit the restrictive particle as a marker of exhaustivity. (Contains 1 footnote.)