Past research demonstrated that age at onset might account for different clinical and etiological characteristics in panic disorder (PD). However, prior research relied on arbitrary choices of age cut-offs. Using a data-driven validated method, this study aimed to examine differences between early and late onset PD in various determinants. Admixture analysis was used to determine the best fitting model of age at onset distribution in PD. Data was collected from 511 individuals (ages 18-65) with PD diagnoses, who participated in the Netherlands Study of Depression and Anxiety (NESDA). DSM-IV comorbidities and various measures of childhood adversities, suicidal behavior, anxiety and depressive symptoms were assessed. The best fitting cut-off score between early and late age at onset groups was 27 years (early age at onset≤27 years). Univariate tests showed that participants with early onset PD were younger and more likely to be female. Early onset PD was associated with agoraphobia, higher frequency of childhood trauma and life events, and higher rates of suicide attempts as compared to late onset PD. Multivariate logistic regression analysis demonstrated that only current age, childhood trauma and agoraphobia remained significantly associated with early onset PD. Findings suggest that 27 years marks two onset groups in PD, which are slightly distinct. Early onset PD is independently associated with exposure to childhood trauma and increased avoidance. This highlights the importance of subtyping age of onset in PD. Clinical implications are further discussed. © 2013 Elsevier Ltd.