We examined whether Anxiety Sensitivity (AS) and Experiential Avoidance (EA), two potentially relevant constructs in the evolution of anxiety and related disorders with significant implications for cognitive-behavioral treatments, differentially relate to symptom expressions of patients with panic disorder and agoraphobia. Within a multi-center study 369 patients meeting the DSM-IV-TR criteria for panic disorder with agoraphobia (PD/AG) completed the multidimensional Panic and Agoraphobia Scale (PAS), the Anxiety Sensitivity Index (ASI), the Acceptance and Action Questionnaire- II (AAQ-II) and the Beck Depression Inventory-II (BDI-II). Overlap, distinctiveness, and predictive validity of AS and EA were examined using explorative item analyses and multiple hierarchical regression analyses. AS and EA moderately correlated with each other (r=-.50, p<.01). EA explained additional variance in PAS-subscales Anticipatory Anxiety and Panic-Related Disability, but not in Panic Attacks, Agoraphobic Avoidance and Health Worries. ASI, AAQ-II and BDI-II explained a low to moderate amount of variation in the five PAS-subscales (R2 =.04-.29; p<.005). AS and EA are overlapping, yet distinct constructs. Results suggest that EA contributes to a significantly improved understanding of vulnerability, at least in patients with PD/AG.