An emerging literature base suggests that symptoms of oppositional defiant disorder (ODD) persist beyond adolescence and are associated with unique psychosocial impairment for adult populations. The purpose of this study is to examine the clinical characteristics of ODD symptoms in a young adult population. Three-hundred and five young adult college students (70.6% female, 66.1% White) completed measures of ODD symptoms, psychosocial impairment, pathological personality traits, comorbid psychopathology, coping and emotion regulation strategies, and service engagement. Regression modeling was used to analyze associations between ODD severity and four domains of interest: impairment, personality, intervention targets, and service engagement. Above and beyond covariates, ODD severity was associated with greater odds of having considered dropping out and reporting more friendships lost in the prior year. ODD severity was positively associated with personality traits of negative affectivity, antagonism, and disinhibition, and negatively associated with psychoticism. Those with greater ODD severity endorsed more coping via venting, and less use of cognitive reappraisal emotion regulation strategies. ODD severity was not associated with past year mental health service use, and was predictive of unfavorable attitudes towards mental health services, above and beyond covariates. Findings from this study suggest that ODD may be a distinct and meaningful disorder for adult populations. Associations between symptom severity and greater negative attitudes toward mental health services may be an important barrier to the provision of clinical services for this population. [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page: http://bibliotheek.ehb.be:2222/en-US/products/dissertations/individuals.shtml.]