The current study explored similarities and differences in parenting stress (PSI) and behaviours in parent reports of autism spectrum disorder (ASD) and attachment disorder (AD). 155 parents whose children had developmental delays and disorders completed the social communication questionnaire, Randolph attachment questionnaire, strengths and difficulties questionnaire, PSI, and parent-child relationship inventory. Parents of children with AD reported greater levels of PSI than parents of children with ASD. Parents of children reaching criteria for both disorders reported the greatest levels of PSI. Limit setting was poorest in parents of children with both classifications, followed by parents of children with AD, and then ASD. Limit setting mediated the relationship between PSI and child behaviour problems for parents of children with ASD < but not for parents of children with AD. These findings suggest different areas of difficulty for parents of children with these conditions, which may be of help in designing interventions.