||Adult extra-textual talk during shared storybook reading can help children learn new vocabulary words. In order to determine what type of extra-textual input is most effective, 3-year-olds heard either scaffolded questions, defining comments, or both scaffolded questions and defining comments about unfamiliar target words during book reading. Children in an ostensive repetition control group were exposed to target words with equal frequency during book reading. Children in all groups performed better than chance on a comprehension test, in which they had to point to the correct picture of a word's referent. On a definition test, there were no differences in the total number of information units children provided across conditions. However, in the scaffolded question group children provided more functional units than in the control group, suggesting that scaffolded extra-textual questions may be most effective for helping children learn elaborated aspects of word meanings.