Purpose This study examined whether there were significant differences between completers and non‐completers of an offending behaviour programme on pre‐programme measures of impulsivity, social problem‐solving, and criminal thinking. Methods Participants were 299 male offenders serving a community order with the requirement to attend an offending behaviour programme in England and Wales. Results The results showed that non‐completers had significantly higher levels of non‐planning impulsivity than completers. Furthermore, non‐completers were at a higher risk of reconviction. No significant differences were found between completers and non‐completers for social problem‐solving and criminal thinking, as well as no significant differences between the two groups for age. Conclusions The findings highlight the importance of retaining high risk and impulsive offenders in treatment programmes.