This paper reports an experimental investigation of presuppositions and scalar implicatures in language acquisition. Recent proposals (Chemla 2009; Romoli 2012, 2014) posit the same mechanisms for generating both types of inferences, in contrast to the traditional view. We used a Covered Box picture selection task to compare the interpretations assigned by two groups of children (4/5 and 7 year olds) and by adults, in response to sentences with presuppositions and ones with either ‘direct’ or ‘indirect’ scalar implicatures. The main finding was that the behavior of children and adults differed across inference types. This asymmetry is consistent with the traditional perspective, but poses a challenge for the more recent uniform accounts. We discuss how the latter could be amended to account for these findings, and also relate the findings to previous results on presupposition processing. Finally, we discuss an unexpected difference found between direct and indirect scalar implicatures.