The intervention study investigated the effects of an interactive word-learning app 1 and picture cards on the vocabulary acquisition of 2-year-olds. Of particular interest was whether or not adult accompaniment during the use of the app or while looking at the picture cards had a positive effect on the child's vocabulary acquisition. The findings show that those children who used the word-learning app when accompanied by an adult had the largest growth in vocabulary, and those who used the word-learning app without adult accompaniment showing the second largest growth. Less successful were those children who played with the picture cards (with or without adult accompaniment). The group of children who focused on the subject matter for the longest period of time on average learned the most new words, while the group who focused on the subject matter for the shortest period of time had the smallest growth in vocabulary.Game apps and learning apps have flooded the market. For caregivers, teachers and parents it has become more and more difficult to identify those that are beneficial for learning (Hartmann, 2014). Many young children use learning apps daily (Common Sense Media, 2011;Medienp€ adagogischer Forschungsverbund S€ udwest, 2012;Rideout & Hamel, 2006). However, research lags behind current practice-there is almost no empirical evidence on the short-and long-term effects on child development of using learning apps. 1 Learning apps are developed to achieve certain aims. In our case, the intention was to enrich the vocabulary acquisition of young children. Many other apps, such as games, are developed mainly for entertainment. The intention of games apps is to hold the attention of the user through exciting or challenging effects, or underlying stories.