According to Russell et al. ("Developmental Rev" 1998; 18: 313) child-parent interaction could contain horizontal qualities, similar to child-peer interactions. To study this, child-parent and child-peer play interactions were compared on several observed horizontal and vertical characteristics in 55 7-year-old children interacting with their mother, father, and a classmate, respectively. Characteristics on which the interactions were compared were shared positive emotions, total control behaviour, balance of control, simultaneous play, mutual responsiveness, and discord. Significant differences between observed child-parent and child-peer interactions were found. Horizontal as well as vertical qualities were found in both types of interaction. The child-parent interaction consisted primarily of mutual responsiveness (i.e. a horizontal quality), and total control, whereas in the child-peer interaction balance of control, shared positive emotions, simultaneous play, and discords were most often found. No main effect of peer preference or gender was found. However, several interaction effects of context with gender and peer preference were found. (Contains 1 table, 1 figure, and 3 notes.)