Background: Previous research has reported on the effectiveness of the Signposts program for supporting families of children with an intellectual disability and difficult behaviour (Hudson et al., 2003; Hudson, Cameron, & Matthews, 2008). This paper reports on an investigation of the extent to which child characteristics moderate the effectiveness of the program. Method: Data collected from 689 participants in the Signposts program were analysed to examine if the child characteristics of gender, age, or associated disability impacted on outcomes. Results: The gender analyses produced mean effect sizes of 0.39 for boys and 0.42 for girls; however, this difference was not statistically significant. The age analyses produced mean effect sizes of 0.38 for children aged 2-5 years, 0.42 for children aged 6-12 years, and 0.30 for children aged 13-18 years; however, these differences among the age groups were not statistically significant. The associated disability analyses across 7 groups produced mean effect sizes ranging from 0.31 to 0.75; however, the differences among these groups were not statistically significant. Conclusions: First, gender was not a moderating variable. Second, while the effect size for the older age group seemed to be marginally lower than that of the other two groups, age was not found to be a moderating variable. Finally, type of associated disability was not found to be a moderating variable. Methodological limitations of the study necessitate care in interpreting the findings. (Contains 3 tables.)