This paper exemplifies a secondary data analysis of context–specific differences in children's hyperactivity–impulsivity while controlling for informant–specific effects. Participants were boys and girls from the NICHD Study of Early Child Care and Youth Development whose behaviours were measured in 1st, 3rd and 5th grades. Latent factor models were structured using multi–informant reports including mothers, fathers, teachers and observers. Temporal stability within a context was stronger than cross–context consistency, and the magnitude of longitudinal stability was higher in the home context compared to the school context. Controlling for informant–specific effects resulted in a significantly improved model fit and increased within–context stability. Our findings highlight the importance of considering both context and informant effects when studying longitudinal stability and change in personality development. Copyright © 2010 John Wiley & Sons, Ltd.