The aim of this paper was to compare the recruitment strategies of two recent studies that focused on the parental influences on childhood obesity during the preschool years. The first study was a randomised controlled trial (RCT) of the Mind, Exercise, Nutrition?…?Do It! 2-4 obesity prevention programme and the second was a longitudinal cohort study. For both studies, the desired population were families with preschool children at risk of developing overweight or obesity. Hence, families from diverse ethnic and socio-economic backgrounds were sought. Funding for the RCT provided the resources to adopt a targeted approach to recruitment whereas for the longitudinal study, recruitment was random and opportunistic, rather than specific and targeted. The RCT reported higher child body mass index-for-age z scores, more families not from an Australian or New Zealand background, and more families in the lowest income bracket, suggesting that strategically targeted approaches to recruitment are more likely to achieve the desired sample.