Young children's positive affect in scripted laboratory procedures and in free-flowing social interactions may reflect the activation of related but distinct aspects of positive emotionality (PE), with different implications for self-regulation. The authors observed children's PE in scripted laboratory procedures and in naturalistic interactions with mothers in 2 studies: at 9, 14, 22, 33, and 45 months (the Parent-Child Study, N = 112) and at 7, 15, 25, 38, and 52 months (the Family Study, N = 102). Measures of self-regulation included effortful control (observed in the Parent-Child Study at 22, 33, and 45 months and in the Family Study at 25, 38, and 52 months) and rule-compatible conduct (observed in the Parent-Child Study at 56 and 73 months and in the Family Study at 38 and 52 months). In both studies, 2 PE measures had distinct implications: PE in scripted procedures related negatively, whereas PE in mother-child interactions related positively to self-regulation. In both studies, those differential effects were particularly clear for children's effortful control. A view of early PE as having a heterogeneous nature may inform researchers' understanding of its role in the developing personality.