Many parents feel uncertain about the actions and experiences their teenage children have on the Internet, thus causing worry and concern. The aim of the study was to examine parents’ worries and concerns in relation to their teenagers’ use of the Internet. The participants were 798 Swedish parents (307 fathers, 491 mothers) and their teenage children (aged between 13 and 15 years). The results indicate that parents’ worries and concerns vary, in certain aspects, according to age and gender of the child. Furthermore, parents’ own Internet skills, experience of using the Internet, and attitudes toward the Internet are related to the type and nature of their worries and concerns. Parents’ beliefs about their teenager’s skills in using the Internet and the teenagers’ Internet use and experiences are related to the parents’ concerns. Parents with an accurate understanding of their children’s negative Internet experiences are those who are the most worried.