This study focuses on mothers of children diagnosed with attention deficit/hyperactivity disorder (ADHD) and sets out (1) to characterize dimensions of both parental functioning (parenting stress and parental practices) and child characteristics (behaviour) and (2) to determine predictors of parenting stress, namely parental rearing practices or perceived behaviour of the child, in order to plan intervention with the families. Fifty-two mothers of children diagnosed with ADHD and aged 6-12 years participated in the study. The Portuguese versions of the Parenting Stress Index (Abidin and Santos 2003), EMBU-P (Canavarro and Pereira 2007) and Child Behaviour Checklist (Albuquerque et al. 1999) were used. Results showed that mothers of children with ADHD experience higher levels of parenting stress (emerging essentially from the child's characteristics) and report more behavioural problems in their children (for girls and boys), but use parental practices similar to those of the mothers of the Portuguese validation sample. Results also indicate that child behaviour (both internalized and externalized) and parental practices dominated by rejection predict parenting stress. These findings have implications for intervention with children diagnosed with ADHD and their families.