This study compared perceived levels of parenting stress between mothers and fathers of children with Attention-Deficit Hyperactivity Disorder (ADHD), children with developmental disabilities, and normally developing children. The relationship of certain demographic variables, such as Socio-economic Status (SES), number of children, years married, parent age, and child age, as well as social support with parenting stress was also examined for mothers and fathers of these three groups. Identification of factors related to parenting stress in fathers was of particular importance for this study, as fathers are often an underrepresented group within parenting research. Identifying effective methods for predicting high levels of parenting stress is important, as stress has been linked to psychological well-being, potential for abuse, and a greater likelihood of poor adjustment for both parent and child. Results from the present study comparing reported stress levels between groups of parents were supportive of previous studies indicating that parents of children with ADHD and developmentally disabilities experience significantly greater parenting stress, specifically with respect to child characteristics. Significant gender differences were also found between mothers and fathers in terms of parent characteristics related to stress. Fathers reported greater stress in the areas of attachment, while mothers reported more parent role restrictions. Additionally, significant negative relationships were found between parents' perceived helpfulness of informal social support and parenting stress scores in both mothers and fathers, affirming positive effects of social support on stress. Helpfulness of informal social support was also significantly predictive of parenting stress in both mothers and fathers across both the child and parent domains of the PSI, although, it had more predictive power with regard to parent related contributors to parenting stress. Family demographic factors, including age of the child and SES demonstrated some predictive power of parenting stress in mothers. Mothers with younger children and lower SES were more likely to report greater parenting stress. Implications of these results and future directions for research are also discussed.