Young children's use of smartphones and tablets is increasingly prevalent. Smartphones and tablets are part of families' daily lives. Therefore, preschoolers are confronted with mobile devices as well, and learn to use them naturally. Specialists who work with children or deal with various aspects of early childhood development are alarmed and warn of resulting harmful effects. It is also feared that research on the impact of smartphone and tablet use on child development cannot keep pace with the rapid technological developments. This review therefore looks at associations between the use of mobile devices and social-emotional development as well as the emergence of behavioral problems in preschool children aged four to six years. A search of the literature was conducted in two databases, PsycInfo and Pubmed. Based on the title, abstract, and in some cases other parts of 861 articles, 7 articles were included.The seven articles are in different research areas, and each demonstrates important research approaches for the topic. An experimental case study with a learning app found benefits for young children's social behavior. On the other hand, a neuropsychological study pointed out that the social dimension of pretend play is missing when playing with a tablet. Other studies, cross-sectional and longitudinal, found certain associations between the use of digital devices and impaired social-emotional development as well as behavioral problems in preschool children and also identified mediators such as parental stress. In sum, however, the results do not provide a consistent picture of the role of smartphone use for social-emotional development and behavior problems in the preschool years. Further research that keeps pace with technology developments is needed.