Objective: A randomised control trial was conducted to assess whether the combined Incredible Years parent training and child training programmes (PT + CT) led to improvements in ADHD-type behaviours in children, when compared to a PT-only group and a Wait List Control (WLC) group. Method: Forty-five families with a child aged 3-7 years who displayed ADHD-type behaviours were referred for treatment and randomised to a combined treatment group (PT + CT; n = 12), a PT group (n = 19) or a WLC group (n = 14). Programmes were delivered by community-based organisations. Short-term follow-up (six months) assessments were undertaken with parents and children based on parent reports of child behaviour and parent well-being and behaviour. A qualitative sub-study was also conducted with parent participants (n = 8) and programme facilitators (n = 5) to explore experiences and views of the combined programme. Results: Statistically significant differences were found between the PT group and the WLC group with regard to child hyperactivity (p < 0.001) and pro-social skills (p < 0.05). No significant differences were found between the combined group (PT + CT) and the PT group except for child hyperactivity (p < 0.05), which was significantly lower in the PT-only group. Significant effects were found for PT + CT versus WLC on the Strengths and Difficulties Questionnaire Impact subscale only. Conclusion: These findings suggest that the combined treatment (PT + CT) produced little added benefit for child hyperactive/inattentive behaviour post-intervention despite the very positive views expressed by parents in the qualitative interviews. The PT training alone was more effective in tackling some core ADHD behaviours when compared to the WLC group, but a need for further more large-scale research is indicated. Trial Registration: ISRCTN82596506.