An online survey of 710 Australian practitioners working in child and family law investigated their views on the best interests of the child (BIC) criteria enumerated in s60CC of the Family Law Act 1975 (Cth). This research inquired about BIC applied to younger (1-2 years) versus older (11-12 years) children. A mixed-model (within and between) analysis of variance demonstrated that 14 of 24 s60CC criteria have more significance for older children. Protecting the child from harm was rated most important regardless of the child's age, whereas the rated importance of a relationship with both parents was more variable. The criterion with the greatest variability for age was "the child's views". Exploratory factor analysis suggested that the high number of s60CC criteria encompass common underlying themes and some redundancy. Findings and implications are reviewed in relation to BIC decision-making and the weight accorded to particular issues by various practitioners.