Objective Recent studies have identified a Child Behavior Checklist (CBCL) profile that characterizes children with severe aggression, inattention, and mood instability. This profile has been coined the CBCL-Pediatric Bipolar Disorder (PBD) phenotype, because it is commonly seen among children with bipolar disorder. However, mounting evidence suggests that the CBCL-PBD may be a better tool for identifying children with severe functional impairment and broad-ranging psychiatric comorbidities rather than bipolar disorder itself. No studies have followed individuals with the CBCL-PBD profile through adulthood, so its long-term implications remain unclear. The present authors examined diagnostic and functional trajectories of individuals with the CBCL-PBD profile from early childhood through young adulthood using data from a longitudinal high-risk study. Method Participants ( n = 101) are part of a 23-year study of youth at risk for major mood disorder who have completed diagnostic and functional assessments at regular intervals. Results Across development, participants with the CBCL-PBD phenotype exhibited marked psychosocial impairment, increased rates of suicidal thoughts and behaviors and heightened risk for comorbid anxiety, bipolar disorder, cluster B personality disorders and ADHD in young adulthood, compared to participants without this presentation. However, diagnostic accuracy for any one particular disorder was found to be low. Conclusions Children with the CBCL-PBD profile are at risk for ongoing, severe, psychiatric symptomatology including behavior and emotional comorbidities in general, and bipolar disorder, anxiety, ADHD, cluster B personality disorders in particular. However, the value of this profile may be in predicting ongoing comorbidity and impairment, rather than any one specific DSM-IV diagnosis.